Perhaps you could find a GPS which gives you access to the mobile app.

I would prefer the option to mark the maps you find with the pen

It's a stupidest idea for this game i have ever heard.It's against the whole concept of using map, compass and knowing your position. If you can play this kind of game like ARMA you won't need this kind of stuff. Besides, there is a GPS in arma 2 and from what i know it will be implemented in DayZ SA too, so if you and your friends will find it, you can easily say one to another EXACTLY where each of you is. Otherwise you have to use the map, and this is most awesome part of the game. I mean in-game map, not any of these lame online maps. It also gives you opportunity to lear how to navigate IRL, cause this aspect is kinda realistic. With your idea, all this would go screw itself.