Reviewed in the United States on March 28, 2018
Summary: The Tello is probably the best performing drone around $100 that you can currently get; flight time and stability in particular are both class-leading. The Tello's controller app now works on all the Apple and Android devices I've tested it on, but I still recommend using an Apple device as you're still less likely to run into issues and may get better performance/range too.
I'll start by saying I'm not a drone expert; I've been interested in them for awhile but haven't actually owned any until just recently. I have, however, been doing a lot of research in hopes of making well-informed purchasing decisions. Other reviews have praised the Tello's great performance, and my own experience with it has found this to be true. As far as actual flight performance (stability, maneuverability, flight time, etc), I'm pretty confident that this drone is the best in its class, and probably by a fairly wide margin too. Friends of mine that own other similarly-priced toy-class drones have commented on how much more stable the Tello was in flight than their drone, and so on. If I had to guess, DJI's hand in engineering the Tello is probably the main reason that the flight performance is class-leading. I will note that, although it is plenty capable for indoor flying, it isn't meant for anything more than light outdoor flying; it has distance/altitude limits well below that of a "real" drone (max of 100m distance and 10m altitude), and is not recommended to be used in any wind (in my experience it can handle a light breeze at most). However, this is to be expected considering it's a lightweight "toy" drone.
Now, the video/picture quality is better than most all other "toy" drones in this price range, but keep in mind this drone is only $100 to begin with (and already excels in flight performance too), so it's unrealistic to expect it to have video/photo quality good enough for serious use. The video is streaming-quality 720p with EIS; it lacks an SD card slot to save directly from the camera, so what you see in the controller app's live feed is what you get in your video recordings. Pictures are better quality than the video (5MP), but good lighting is necessary if you want them to look decent. Again, this is just a lightweight "toy" drone that costs only $100, so don't have unrealistic expectations and think it can replace a "real" (and much more expensive) drone for cinematography/photography.
As far as the Tello's app/controlls go, I never had any issues when running the Tello's app on a 2017 iPad, and I'd imagine that any comparable Apple device would run it just as well. I had zero real issues controlling my Tello from the app on my iPad, even with multiple other wi-fi routers/APs in the area, and the lag, although present, was reasonably low. Again, as a "toy" drone in this price range, it's unreasonable to expect it to come with high-end radio signaling and/or a hardware controller with a dedicated link that would allow for super low latency control, but I never felt like the app controls had enough lag to really inhibit my control of the drone. However, I must say that, when I first tried it on two of my Android devices (Nexus 9 & Nexus 7), I wasn't even able to get the app to start without crashing. Now with a updated version they have since released, it currently works fine on my Nexus 6, although the video quality and range is a bit less than it is with my iPad. Your experience may vary depending on which Android device you have, and it's possible you could get performance comparable to what I got out of my iPad with another Android device, so I'm not going to say that Android device owners shouldn't try it. However, Apple devices tend to have more consistent hardware and software, and it's also likely that Ryze put more effort in to the iOS version of the app than the Android one, so overall I still recommend using an Apple device if you can... there's a good chance it will work better with one.
Also, there is something else to note about the Android version of the Tello app; namely, I'm concerned by the amount and kinds of permissions that it has... many seem unnecessary and even suspicious for an app that (should) just have the job of being a remote control for a wi-fi drone. (Below the body of my review I have a list of the (IMO) most concerning permissions.) It's unfortunate that it has (or at least tries to get, depending on the version of Android your device has) all these permissions which could allow for collecting metadata, even in the background (when you aren't running the app). And Ryze being a relatively unknown Chinese company makes it all the more concerning. Now, I'm not saying they are definitely collecting metadata (I haven't done any technical analysis of network traffic/data or such to prove/disprove it), and some of these permissions it requests could be used for compatibility with older versions of Android, but it is still rather suspect IMO, and because of it I have refused to install the app on my main smartphone (or any Android device which may contain personal data/accounts). On the flip side, I don't have to worry about this with Apple devices, since iOS doesn't allow apps nearly as many permissions in the first place, and even the ones it does have the app must always ask for permission first. FYI, the only permission it asked for on my iPad was location, and I denied that and the app still worked fine anyway (Tello is not a GPS-capable drone, so other than maybe for geotagging your photos/videos, there isn't any reason it needs to know your location).
All-in-all, if you're looking for a fun but surprisingly capable little "toy" drone to fly indoors (or outside only with little to no wind) and don't want to spend much, I recommend the Ryze Tello. I recommend it even more-so if you have an Apple device to use with it; in fact, the reason I rated it 4 stars instead of 5 was because of my privacy concerns and some issues I had with the Android app (if they remove those permissions and continue to improve the app, I will consider updating my review to 5 stars). On a side-note, if you are looking at getting in to drone piloting on a more serious level, I would not recommend this in place of a "real" drone... it may set new standards for the capabilities of "toy" class drones, but even a very good "toy" class is not enough learn real drone piloting. (For a beginner drone for serious drone piloting, I would highly recommend the DJI Spark instead, as it's (IMO) currently the cheapest drone with serious flight capabilities). In my case, I bought this in addition to the "real" drone I already had, so I could use it for indoor and casual flying (rather than risk my main drone).
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List of potentially concerning Android app permissions:
- access precise GPS location - the Tello does not use GPS so no reason knowing my precise location should be needed for flying-purposes... perhaps for geotagging photos/videos maybe, but once the app has this permission there's nothing preventing them from collecting my position data either
- read phone device ID - with this it could read your phone number or IMEI/MEID; older Android apps used to use this to get a unique device ID or check your mobile connection, but newer versions of Android have better/safer ways of doing these, so there's little legitimate reason for them to need this permission now-a-days
- see all running apps - uh, no good reason it needs to know what other apps you are running
- run at startup - why does it need to automatically run in the background when it's just a drone controller app... unless it actually does this so it can gather information constantly in conjunction with the other permissions it has... definitely suspicious.
- modify system settings - it's possible they use this to try to help automatically configure wi-fi/bluetooth/controllers for you but it's still concerning
- android.permission.MANAGE_ACCOUNTS - this is a permission that was used more on older Android versions; it's unclear what exactly this allows the app to do on newer Android versions (it may be harmless), but since this is a newer Android app they shouldn't need this permission anyway...
- read Home settings and shortcuts - why? ...this is random and without a doubt entirely unnecessary
