Suggestions for ISP failover

Currently we have a T1 into a pix 501. What we need is to ensure as much possible uptime as we can. It has been suggested to me that we look into a failover system between out T1 and a static dsl line.
Anyone have any experience in this or suggestions?
So far I have been looking at an appliance from astrocorp, and setting up pfsense as a load balance server (failover is buggy atm in pfsense).