After 201 days in App Store approval purgatory, TrapCall is finally available for the iPhone. You pay $5/month, and the service will tell you the name and number of whoever calls you from a blocked number. How does it work?
Here's what 9to5Mac says:
When you get a call, press the power button twice to decline it and let TrapCall do the unmasking. Within seconds the service sends back the call to your phone with the number unmasked along with the name and address associated with the caller (when available) via a text message or push notification.
The service will even block incoming calls, transcribe voicemails and can play a voicemail greeting informing the caller that your number has been disconnected. Definitely seems a bit sketchy, but if it survives in the App Store, it's a nice way to separate the random telemarketers who are harassing you, and your friends who are just paranoid. [iTunes via 9to5Mac]