At least the makers of are telling. Despite "great discussions with senior Apple executives at their Cupertino headquarters," the Tawkon team Apple ultimately rejected the radiation-detecting iPhone app. An appeal to Apple Chief Executive Steve Jobs went nowhere.

"No interest," Jobs reportedly wrote in an e-mail to Tawkon.

The Tawkon app measures a phone's Specific Absorption rate, environmental factors and physical position to determine how much radiation you're soaking up. It then provides tips, along the lines of "hold phone vertically" or "go back" to your previous location.

Neither Tawkon nor Apple are saying why, exactly, the app was rejected, but the issue could be the amount of information third-party iPhone apps are allowed to access. Tawkon's blog does mention that Apple "explored various technical solutions with us to overcome API restrictions," so my guess is that Tawkon needed to access certain data that most apps can't have, and Apple didn't want to relent.

Of course, that's not a problem for jailbroken iPhone apps, so with Apple's rejection, Tawkon took its app to the Cydia app store. It's also available for select Android phones and Blackberry phones.