You may have good reason to safeguard your privacy these days, but would you hand over the goods if someone paid you? For some people, the answer is "yes." Companies like Luth Research have been paying willing subjects a modest amount (in Luth's case, $100 per month) to track their devices' locations, web histories and app usage to improve advertising and shopping. Ford, for example, used the technology this year to see how prospective buyers research a car; it could tell if participants bought a vehicle after visiting its site, or if they were using their phone to research alternatives in the showroom. These monitoring schemes are hardly low-profile, either. Verizon recently launched a voluntary program that promises rewards if you share your positioning and web info.