High availability using heartbeat s/w across a WAN

Hey guys, im currently doing some research on implementing a high availability system across a WAN link and would like help on certain areas. This is a scaled down project so I might end up using router simulators like gns3, vyatta etc instead real hardware. Also it'll involve two webservers on each side on the WAN(actually both server's will be next to each other so it's more like a fake WAN connection).

First, from peoples exprience, what are good choices of WAN connections (frame relay, leased lines etc) for such a system since failover is mostly dependent on the heartbeat monitor?

Second, is it even possible to transmit heartbeats across the WAN. I'm sure latency will be a concern but like I said this is scaled down and is for testing..

From read linux-ha.org's tutorials, I found that most setups are on same LAN and a serial(RS232) connection is used between the servers/machines.

In precis, I want to be able to achieve failover across a "fake WAN" (if you like).

Any responses or even pointers will be appreciated