This actually sounds pretty amazing. Apparently this "imFONE" USB device allows you to use your existing cellphone as a VoIP phone. You simply plug this thing into your PC's USB port, pair it via Bluetooth to your phone, and you're ready to go. We're not too sure on how you're supposed to make calls "via IM" since it's really VoIP (there was no mention of using this via Google Talk's chat feature nor iChat AV). It currently works with imtel and Skype, which of course means cheaper calls as you avoid all that hassle of counting minutes. But the primary advantage of using your existing cellphone is that all your contacts are already on your phone, and your cellphone number will be displayed on the caller ID on the other side. This really does sound enormously useful, especially if you use your cellphone as your primary phone, and if you travel a lot (No more roaming fees!). Unfortunately, we're not able to find how much this thing costs, if it'll be available outside of Korea, and we're not too sure which phones this thing works with either.
IM Fone - Bluetooth based device allows using cell phone to make calls via IM