I have been looking at the various plugins to dial phone numbers, send sms etc. What I am hoping to accomplish is the following:

I have a system to checkout equipment to students. If they are past their due date, I want to use a plugin to send a recorded message stating that their item is overdue.

Has anyone had experience with this.

I chose this route as... some students do not check their email often enough, some do not have unlimited messaging and still other are not using twitter, etc.

or....If you have a different suggestion of integrating contact info with a reminder system... I am indebted.

I once did something very similar with ovolab's Phlink. Their software is very cool and with it you can initiate an outgoing phone message. It requires the use of their own hardware (modem) and works with Mac. Google them, and ask if Phlink can do exactly what you want, just to be sure, before you buy it.