Interesting- it can be used with .gpx files downloaded to the phone. All gps file data uses this format. There is no reason, in theory anyway, why you cant overlay the .gpx data over any mapping software and have it place you correctly. Which makes following "off-road" routes a possibility, I reckon. Of course, you need the file data in the first place to do this, obviously...
I bought one recently too. For the motorcycle. Used on the road only so far. Im not used to its directions yet so made a few navigational errors. Found it hard to get it to "re-route" effectively once following a "planned" ride ( designed by waypoints then) after you go wrong. teething problems I hope.... but I did come across some of the best roads around here in "fun" mode...so its not all bad.
The iPhone gets too hot in Europe to work effectively on the handlebars..plus the screen is mostly useless in daylight most of the time...And I havent found a way to power the smart phone without compromising it's weather resistance. It seems to need a cable which compromises the weather cases...or you run it out of power in a few hours with screen on..pretty useless then, honestly. Riding green lanes can see you needing realtime directions at quick pace..more like a roadbook ! So the Beeline offers a solution to some of these issues. The Velo version just has different buttons to the motorcycle unit I think. No mapping differences then....