Just bought one of these on Ebay for UKP 35 + P&P (it's probably possible to get it cheaper by careful bidding, this was a buy-it-now price).

The device logs data to internal memory, as well as providing Bluetooth connectivity for external devices. There is a single button on the front which logs a waypoint, and a dual mode switch for Bluetooth only / Bluetooth + logging.

The software supplied with the device isn't very useful, but a quick internet search revealed the excellent (and free) BT747 software (for both the PC and my mobile (Sony K800i)) which allows advanced configuration. I'm only interested in lat and long, not elevation, speed, etc, and I'm logging HDOP (which JOSM will display in the GPX trace). The version for mobiles allows me to monitor satellites, as well as recording waypoints and change the device's configuration, reset it, etc.

I've been experimenting with using it in tandem with my Etrex Venture Cx, which being the older, lower sensitivity receiver, I've been having to take multiple readings for many paths. Dual GPS receivers should help with getting more accurate readings and save a bit of flogging up and down.

All in all, the is a very cheap way of logging reasonable quality data - the addition of Bluetooth allows external monitoring and configuration, and you can extract the data later on a PC (or even on the go from the mobile).