Hi,
I would like to create and application for android that shows the
location of the phone on the a map - just like a GPS device.

I did some reading on the Location-based Service APIs and the MapView
classes. But still not sure how or where to start.

I'm not sure but maybe there is an open source code for what i need,
or part of it..?

I would appreciate any help i can get,

Thanks

There's a lot of advice in the Maps forum.
Also, you can search for AndBook here in AndDev; it will help you a lot.