Wow, this is an old thread
There are several different options right now for what you want to do. For example, the Phidget SBC, our own single board computer solves many of the problems people have, wanting to use phidgets wirelessly. If you just wanted to use a cellphone by itself, that's a little more difficult. The phone needs to be able to act as a USB host for another device. I don't think there are any cell phones out there that do that yet. However, it's actually not that difficult to plug a standard cell phone into the SBC and use it as a modem to stream data. Of course, wifi is also really easy to do with the SBC too. It all depends on the range you need.
The only issue you're going to have with running through wifi, or 3G is latency. You likely wouldn't be able to control an RC helicopter in real-time, but if you're creative enough with programming, you could possibly have the helicopter fly itself. It's sort of a goal to have the RC helicopters and airplanes littering the office around here, actually fly themselves.
We have started working on some wireless adapters for phidgets, but don't get too excited about seeing them on shelves any time soon. They're still VERY early in development.