Re: Control electronics
You're most certainly going to need an IAS (Indicated Airspeed) sensor. Real airspeed is not actually measurable directly. Speed over ground, as indicated by a GPS is completely useless unless you know the exact windspeed of the air around the plane, which you don't. (In strong winds, speed over ground can be 0 or even negative! Especially for a light craft such as LOHAN.)
Yes, airspeed sensors for RC applications are already available for large scale RC gliders. They even have Total Energy compensated variometers nowadays.
For altitude, a barometric pressure sensor is going to be much more accurate at giving you an altitude than GPS. General rule of thumb, GPS is about 5 times less accurate in altitude as it is in horizontal position. This error increases further at greater altitude and most commercial GPS chips have a hard time even getting a good fix above 15 km or are programmed not to give data above this altitude (the US considers any GPS chips capable of getting a good fix above 18km to be weapons components, specifically guided rocket components, and bans trade of components and knowledge thereof under ITAR regulations. the LOHAN D-CUPS team might find this link interesting: http://bear.sbszoo.com/construction/gps/LP/LP_GPS.htm).
Surprisingly enough, barometric pressure sensors are pretty damn accurate. More so than GPS at lower altitudes (So for landing control and such, you'd want a pressure sensor).
Using a smartphone instead of a dedicated electronics platform (the UAV-dev and Ardupilot boards being prime candidates) is not really going to provide much advantage. Coding is often more complicated, not to mention actually linking the thing to I/O's . The accelerometers in smartphones are often not that precise and suffer from quite a bit of jitter. Not really noticeable when controlling a game on a smartphone, but enough to cause problems in a controls-algorithm. Most UAV boards have high-precision IMU's (Also handy for dead-reckoning in case of loss of GPS signal. More accurate IMU means better navigation accuracy in that case)
Beer: because I'm slightly inebriated while typing this.