Hi..., what a curious question will be what mobile platforms are u targeting eg. Android, Symbian, Bada..?
but on general terms..
on server-side you'll want all the services/places stored in the system with geo-position attached.. best db for this is Postgrel, Mysql works too, and even sqlite support spatial data now..
u'll definitely need Google Map Api for your own visualization and easy tagging of places instead of manually entering coordinates.
i have now idea on how u planning on the interaction on the mobile part. But either it be a plain string response or a full map viewer, u'll have to figure out to capture ur on gps position and send to the server which will return nearby marks.
More info:
links:
--
Allen Machary.