Gordon Meyer writes in PhoneValet & iPhone: Instant Landline Voice Mail:

“Parliant’s PhoneValet has been a valuable part of my automated home for a few years now, but the recent addition of built-in iPhone/iPod touch support has pushed it close to a “must have” tool.

PhoneValet has long had the ability to answer the phone, present a simple (or sophisticated, if you’d like) voice mail system, and record messages. It’s also been able to send email notifications of incoming messages and, more recently, offered a web-based interface to view call logs and play voice mail via the PhoneValet Anywhere add-on.

But for me, it took the iPhone to gel all these pieces into a coherent and very useful whole.”