It is definitely doable, but probably not out of the box - you need to make n810 to open service over SPP profile on BT and feed there internal GPS data. Probably it can be done in a simple bash script, but you have two problems:
1. n810 GPS device is just... not the best (especially taking into account time-to-fix)
2. n810 battery might die quite fast
I really think, that buying ANY bluetooth GPS receiver (they are really cheap now) might be just better choice.