I only just discovered multicopters this week - amazing machines!!
As a kid, I used to build lego robots and hook them up to my old BBC B with heavy cables (which always pulled them off course) but I'd been thinking of getting back into robotics with my own kids and I'd already been thinking about using an old Android phone as the brains of a robot and making full use of all its built-in sensors (GPS, accelerometers, orientation, proximity, light, sound etc.) and its camera, possibly in conjunction with all the cloud based services for OCR, face recognition, voice recognition etc.
Now I'm thinking that a multicopter with a phone as its brain would be perfect! I could have a tablet or laptop connecting to the phone via Wi-Fi (perhaps with a ground based Wi-Fi router), for both control and streaming video. However, looking at all the amazing projects on this site, everyone seems to be buying separate sensors, cameras, video transmit modules etc, and using Arduino as the brain. This looks like it works really well, but I would think that a phone would work out a lot cheaper and probably lighter, so my question is, why is no-one else doing this? I can't possibly be the first person to think of it, so I guess I'm missing something, but it would be great if you could enlighten me!