Question : Redundant Internet Connection with OSPF

Here is our setup:

LAN A --- 3560 A --- PIX A --- Internet
                   |
     34Mbps Wireless Link
                   |
LAN B --- 3560 B --- PIX B --- Internet

Currently we have everything setup with static routes. What I would like to do is implement OSPF for our network. Along with this I would like to be able to add some redundancy to our internet connections. So if the internet at LAN A went down it would automatically switch over to use the internet at LAN B. I know this would be slower as it is going over the wireless link we have between the 2 buildings but its better than nothing. I know how to configure a single area OSPF network. But I have two questions:

1.) How will OSPF know if one of the the internet connections go down?
2.) How can I make it use the local internet connection and only switch over if one of the internet connections go down?

This may be a simple fix but I just have not been able to wrap my head around how to accomplish this.

Answer : Redundant Internet Connection with OSPF

use route-tracking but for this you need to be able to ping one device in the ISP network.
http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/products_configuration_example09186a00806e880b.shtml