Maemo Mapper is already using this API (if you use "File Path" in the Settings dialog). It doesn't seem to work with the built-in GPS on the N810.

Maemo Mapper also supports libgpsbt, which is used if you specify "Bluetooth" in the Settings dialog. Normally, when you do not specify a MAC address when using libgpsbt, Maemo will automatically search for bluetooth devices that claim to be GPS receiver. For some reason, there seems to be a feature (undocumented?) that allows causes libgpsbt to work directly with the internal GPS receiver if you don't specify a bluetooth MAC address. I have no idea why this works, but it does.

I can't investigate further until I actually have an N810.