Incoming GPX would be Tracks & Waypoints
Outgoign GPX would be Waypoints &, potentially, Routes
'Database' would tun in a Virtual Machine (to be easily replicated in different offices) & would consist of:
* PostGIS
* Mapnik
* Sahana Eden
* Potlatch2
* mkgmap
More detail:
http://eden.sahanafoundation.org/wiki/BluePrintGISGPSSharing
Integration Platform
Display WMS, KML & Internal Resources over an OpenStreetMap base layer (or Google, or Yahoo)