A smartphone app will do this fine. With an iPhone, I used the Cyclemeter and B.iCycle apps which worked great. The main limitation was battery life (~3hrs) and the fact that you can't download a course to ride. Handlebar mounts are readily available, even water resistant ones if that's a concern. I've since switched to a 705 because I can plan rides and download them for course guidance. BTW, the display and mapping on the iPhone is way way better than on the 705, but mapping requires data connectivity.