I'd suggest starting by jotting down some pros and cons of teaming up with them. What do they bring to the table? What are the holes in their business plan? Is there a complementary fit with your skills? What is the "pain" they are addressing with their proposed product? Do they know the right people in this industry? What are the prospects for a successful exit (e.g., via acquisition by Garmin)? What if that acquisition requires you to join that company for several years?