Re:
Are you talking about harware or software?
Software wise, I just use the basic Strava app for iPhone. Although I've looked at others (MapMyRide, Ride With GPS,etc), I've never used any of them, but Strava seems to work perfectly fine for my basic wants of seeing how far I've gone/climed, and my times over route and segments. I can measure my own improvements from there. Benefits for me are the volume of users and uploaded information from other local riders, allowing setting personal targets etc. The iPhone app is a wee bit limited imo in terms of functionality, but the full desktop site addresses a lot of these issues (e.g. planning routes, etc).
Hardware wise, I dont bother with heart rate monitors (yet!), but I've been thinking more about investing lately, and may upgrading to Strava Premium to support this.