I'm looking for sources of inspiration for developing new apps & am wondering which existing apps do you consider to be the most innovative, in terms of exploiting the functionality that the smartphone platform offers?<p>Some examples:<p>Bump [YC 2009]: Combines location + accelerometer to match and connect bumping phones<p>Shopkick: Uses ultrasonic sound to confirm entry to shops and then offer rewards<p>Several pulse meters that are based on camera observations<p>etc