Callfire is on twitter pimping "Try out pay as you go IVR to create custom appointment reminders or notifications! http://bit.ly/9Xnd6E"
Ifbyphone is also on twitter pushing IVR-in-the-cloud. And XO has an IVR-in-the-cloud app.
These are stand-alone, no contract services. Seems like the Hosted PBX folks should be pushing this feature too.