"Interesting thought. But I can't sample TV signals from a mobile device. " You couldn't sample FM radio or GPS from them in the past either :) But honestly,

"Interesting thought. But I can't sample TV signals from a mobile device. " You couldn't sample FM radio or GPS from them in the past either :) But honestly, i don't expect this to take the world by storm either, i'm just pointing out it's a better possibility of working for the use case of "indoor mapping". " I'm looking at applications that can be implemented underground as well, unique use case. And in this case, proximity might be just fine enough rather than positioning." Underground is really hard, yes. If all you care about is knowing you are within 40 feet, great. Truthfully, specialized wifi points are likely to be better for indoor positioning than bluetooth.