I've recently been thinking again about a product that Viprinet provide, basically they've got a pair of routers, one that lives in a datacentre, Their VPN Multichannel Hub and the on-site hardware, their VPN multichannel routers

They've also got a bunch of interface cards (like HWICs) for 3G, UMTS, Ethernet, ADSL and ISDN adapters.

Their main spiel seems to be bonding across different media. It's something that I'd really like to use for a couple of projects, but their pricing is really quite extreme, the hub is about 1-2k, the routers are 2-6k, and the interface modules are 200-600 each.

So, what I'd like to know is, is it possible with a couple of stock Cisco routers, 28xx or 18xx series, to do something similar, and basically connect a bunch of different WAN ports, but have it all presented neatly as one channel back to the internet, with seamless (or nearly) failover if one of the WAN interfaces should fail.

Basically, If i got 3x 3G to ethernet modems, and each on a different network, I'd like to be able to loadbalance/bond across all of them, without having to pay Viprinet for the privilege.

Does anyone know how I'd go about configuring something for myself, based around standard protocols (or vendor specific ones), but without actually having to buy the Viprinet hardware?