Network Failover / Bonding

I have a Linux box that has a few different connections to wans and one to the LAN.

Example:

workstation 1 \ / Wan 1 (wired)
--- Linux Router -- Wan 2 (wireless)
workstation 2 / \ Wan 3 (USB wired)

What I need is a script that can set up the wans to load balance / failover if one goes down or is added/removed.

Right now, I wrote a script that does the following:
when a new wan is added/removed, it relaunches Dispatch-Proxy with the new IP
routes the LAN users through redsocks proxy -> dispatch-proxy

Its been working but its not very reliable. I have to restart dispatch-proxy a lot it doesn't really detect if a connection is lost etc..

I am not sure the best way to do this or set it up so if you think you can help give me a shout.

Thanks