Does anyone know of or use an app that will auto-enable a bluetooth tether when wifi isn't connected & vice-versa?

I'd like to have my Transformer Prime on line at all times, choosing the best available connection. If I go out of range of a wifi connection, I'd like it to automatically connect to my Razr via bluetooth.

I can obviously do it manually, but I hate having to go through multiple steps on two devices when I need internet on the tablet. I'd like it to be relatively seamless and "backgrounded".

I looked at having Tasker do this, but it isn't capable of activating a specific bluetooth connection - it can only toggle the bluetooth radio on or off.

Any ideas would be welcome.