CallWave Visual Voicemail is a free service that lets you manage your mobile phone messages on your computer. It’s designed to work with virtually any cell phone, and on virtually any network, and sends copies of your messages to your email inbox, where they can be played, paused, replayed, saved, and deleted. If you’ve ever lost a message after the 14 day period that your phone company gives you, this service is for you.
If a widget is more your style, then check out the Visual Voicemail Widget for Apple, Yahoo, and Vista. Each one alerts you to incoming calls, and gives you call details like the length, and when it was received. Give CallWave Visual Voicemail a shot, and think outside the Phone (or iPhone in this case).