Fully functional GPS receiver on your wrist
Note that this review is for the full version, which I purchased as an upgrade from within the lite version. Mark waypoints, track your movement, view previous tracks, get a bearing to a waypoint, import GPX files, use topo maps offline - this app does it all, without needing to be connected to your iPhone (except for importing exporting, GPX files). Developer is also quick to respond to inquiries.