Here are two solutions that 100% work (the nosleepraphael cab does not work and may change your polling to 1000 which isn't good):
This one works on orientation so during a call if the phone is vertical then the screen is off - turn it face up and the screen comes back on:
http://www.fuzemobility.com/in-call-...solved-really/
this one is the traditional method where it stays on and then dims after 1min:
http://www.fuzemobility.com/in-call-...-solved-again/