Fulcrum Designs has been developing satellite navigation devices for some years now and has created vehicle tracking and remote guidance devices. The accuracy of GPS is steeped in myth and here-say but put simply it's repeatability in open area is far better than the cautious claims made by chipset makers. In urban situations it's not so good but with augmenting services is acceptable for virtually all applications. The imminent commissioning of the European Gallileo system will allow far greater accuracies to be obtained than the existing US military GPS system.
Fulcrum Designs only work with the very best chipsets (currently SiRFstarIII) and can use the outputs of these devices to send, record or display position data.
Position can be used locally to guide the user, or it can be sent via any manner of radio systems from low power short range (200 metre) devices through to global mobile phone systems.
GPS use in a logging function is many and varied and data can be saved via SD cards for later analysis. All manner of data can be saved at the same time to create a full snapshot of a particular event or set of events.