Today I tested the Holux M-1200 gps logger.
The device looks very robust, I didn`t read any info about water resistance, but if you plan to mount it somewhere under the windshield should be ok. It has an “on-off” button and a button for marking a POI. The three leds mark gps connectivity, battery status and bluetooth connection. Regarding the functionality, is exactly what I wanted, it silently logs your position. A nice feature is that you can select the position to be logged either after specified number of seconds, or distance in meters, which is a very nice feature.