I have recently acquired a Garmin 310XT watch.
It seems to be a great option for speed windsurfing:
record every second
great capacity and battery life
configuration of screen
price just a little higher than a Navi GT + aquapac
it is a watch! a bit big though :-)
I have also noticed that Garmin is now recording the speed every second and this information is available in their .fit file format. After a few analysis using GPSResults it seems that this speed if much more accurate than the one calculated from the GPX file (using the position)
I have asked Garmin on their forum what is the source of this speed. For the moment my question is unanswered but it might be the doppler shift value.
There are numerous API that have been designed to read the .FIT file format and I was thinking that it would be a good idea to support this file going forward.
Let me know what you think.
PS: Python API https://github.com/dtcooper/python-fitparse/tree/ng
.FIT SDK http://www.thisisant.com/resources/fit