Dakota Alert - wireless, great product, you'll be amazed at the range
[Link: dakotaalert.com]

The Dakota DC powered receiver has dry relays you can wire to whatever. You can have multiple receivers on one project. You can have 4 senders to one receiver, based on setting dip switches. And you can turn off the volume tone on the receiver if all you want is the integration part.

CarTell - the wired standard - http://cartell.com/