The GVMate is a relatively unknown USB dongle similar to the magicJack. It costs just $29.95 and works in tandem with Google Voice (via any Gmail account). It is very similar to the much more expensive OBihai OBiTALK devices and it provides free calls forever to the US/Canada and incredibly cheap international prepaid calling rates, just like FreedomPop phone.
Anyone with a US Gmail account can make free calls from their computer and Gmail via Google Voice but the GV Mate dongle allows you to hook up any regular phone and use Gmail and Google Voice, thus turning your Google Voice service into a regular landline VoIP telephone. Without the GVMate calls can only be made via your computer and Gmail account. In addition to this people outside the US can make free calls to any US/Canadian number.