Phone Amego is a clever little menu-bar app that integrates your iPhone--or other Bluetooth phone--with your Mac and with the Google Voice service. At its most basic, Phone Amego provides onscreen caller ID (a small window on your Mac displays incoming callers, and you close the window to send the call to voice mail, or you can program it with AppleScript to respond when you speak the name) and enables you to call contacts from your Address Book with just a couple of clicks. There are also basics like a call log, timer, and a hot key for answering calls. You can place calls from Phone Amego's Call window, or via Quicksilver or LaunchBar, and you can also dial almost any number on your screen using a contextual menu, although you have to activate this OS X service ability manually in System Preferences. Phone Amego supports Growl notifications, and you can receive SMS messages in iChat.
Phone Amego gets even more useful if you have a Google Voice account: you can make Google Voice calls, and you can send free Google Voice SMS messages to multiple recipients directly from Address Book. This app can also execute scripts based on your phone's status, including several useful ones that come built in, such as muting iTunes when you take a call or changing your iChat status when you get on or off a call. This app is still growing, but if you spend a lot of time simultaneously on your phone and your Mac, Phone Amego's useful features, good documentation, and responsive developer make it a worthwhile investment.