The problem with social network check-in services is that they are not very accurate when you are somewhere without GPS coverage such as in a building like your home, office or shopping mall. Researchers at Northwestern University’s McCormick School of Engineering and Applied Science developed a very interesting technique that uses acoustic fingerprints to identify locations in areas where GPS location information is not available.
If you have an iPhone, iPod touch (recent model with a microphone) or iPad, you can test this for yourself using a free app developed by a graduate student working on the project.
Batphone (iTunes App Store)
The app samples 10 seconds of sound where you are standing. Then, you can name your location (kitchen, my office, etc.). I found it surprisingly accurate even when sampling in locations that were very quiet: No traffic noise, no motors and no one speaking. It was able to differentiate areas as close together as 10 feet despite the lack of obvious ambient sound signatures.