I use a Garmin GPSMAP60C. I have found this to be the most useful training tool for someone like me who train alone most of the time, and who has to troubleshoot his own technique on a regular (read ongoing) basis. I have it mounted on my Mako Millenium right between the foot pedals on the foot straps where it is easy to reach. I used the mounting bolt from the strap
through a Garmin Marine mount, so minimal risk of it comming off, and I secure the lanyard around the foot strap as well. The Garmin suction cup mount is also quite secure from what I hear.
The unit can record your route in a number of forms; set time intervals (from 1 sec to multiple hours), set distance (every few meters/yards to every hundred kilomters/miles), and if I remember correctly direction changes (set number of degrees).
The GPS comes with basic mapping software (includes downloading) and a USB cable. I export the data as a text file into Excel for graphing and subsequent geeking. I have purchased a couple of sets of Blueways Nautical Charts (Western Canada adn Hawaiian Islands) that I uploaded to the GPS from my PC. There ase ~$150 CAN per chart set and excellent resources when checking out race venues, water depth, possible currents, routes, hazards, etc.
I’ve posted some other info and sample maps, data (2004 Tour of Indian
Engineered Athlete Services