[Zope] suggestions for what to run in front of ZEO'ed zopes for failover?

I'm wondering if anyone can suggest something good to run in front of 2 zopes talking to a zeo server - for failover and load balancing. I have been using a tool called 'balance' which works really well - but for failover it only works if the socket to one of the zope servers doesn't connect. We occasionally have a situation where the socket will still answer but the zope server hanges and never returns an answer. So, I'm looking for something with configurable timeouts on responses. Does any one know of anything like that? Thanks, ^Roman