It took me a while, but I actually got mine to fail back automatically. I have two connections at each site, but at the main site I'm using both connections, one for internet and the other for vpn's. The vpn's can fail back to the internet connection if needed.
At the remote sites I setup the primary connection with a tracked ip. When it goes down it brings up the route to the other connection. As soon as the other connection comes back up it switches back to the other connection. What really threw me for a loop was I could access my main site just fine from the remote site, but I couldn't access my remote site from my main office over the new connection. I finally figured out I had to add a tracked route for the remote ip address range over the second interface. When it's up it sends the traffic over it and when it goes down it sends it back over the 1st interface. Otherwise even with the tunnel up on the new interface it was trying to send the traffic over the internet connection.
Additionally, on the ASA 5505's I found that you can't just enable a 3rd named interface. To do so you have to restrict access to the other outside interface and you have to name it from the command line.
Thanks for the help!