Postgresql high available solution

Hi,

we would like to switch from mysql cluster to postgresql. We need high
available solution so we can store telco data for our PBXes. The
problem is, we dont know what would best suit to our needs, we need:

1) High availability with failover - if one node goes down, nothing
bad happens (<5sec downtime)
2) Load balancing (actually we have 90% SELECTs and 10% update+insert)
3) No query based replication (we often use current_timestamp(), now
and other functions which could generate different values on different
nodes), this can be problem with query replication, is that true?
4) GUI for administration

What replication software or other tools would you recommend for this
setup? Or do you know some professional (or company) which could help
us to deploy such system?

Thanks,
Mino Haluz