I have the Edge 305 and you can set your starting point and it will tell you what direction to get back or you can bactrack your course but their is no mapping software. It is a great cyclometer with a lot of features but I also have the Garmin Etrex Legend
http://www.garmin.com/products/etrexLegendcx/
which sounds more suited for what you are looking for. You can put in your starting point, drive 50 miles, get lost and then tell it to route you back and it will give you turn by turn directions. You can get the bike clamp and it runs on AA batteries and gets decent battery life. It will give you basic functions like speed distance time and that type of info. If you need mapping software then this unit is pretty good and durable.
If you want a nice cyclometer that you can use to give you the general direction you need to go then the Edge 305 is one of the best out there.
Kenal0