You might want to keep your cell phone in the fridge...

Or between some lead bars...

Post hijacked from Bruce Schneier from Schneier On Security:

A service called World Tracker lets you use data from cell phone towers and GPS systems to pinpoint anyone’s exact whereabouts, any time — as long as they’ve got their phone on them.

All you have to do is log on to the web site and enter the target phone number. The site sends a single text message to the phone that requires one response for confirmation. Once the response is sent, you are locked in to their location and can track them step-by-step. The response is only required the first time the phone is contacted, so you can imagine how easily it could be handled without the phone’s owner even knowing.

Once connected, the service shows you the exact location of the phone by the minute, conveniently pinpointed on a Google Map. So far, the service is only available in the UK, but the company has indicated plans to expand its service to other countries soon.

[...]

Dozens of programs are available that’ll turn any cell phone into a high-tech, long-range listening device. And the scariest part? They run virtually undetectable to the average eye.

Take, for example, Flexispy. The service promises to let you “catch cheating wives or cheating husbands” and even “bug meeting rooms.” Its tools use a phone’s microphone to let you hear essentially any conversations within earshot. Once the program is installed, all you have to do is dial a number to tap into the phone’s mic and hear everything going on. The phone won’t even ring, and its owner will have no idea you are virtually there at his side.