While searching for good DNS providers and hosts we stumbled upon:
We haven't been able to find a single DNS provider that offers this type of functionality and they even do it completely free of charge.
All with an great easy to use interface.
The only issue is that we have not been able to contact the developer to see how active the project is. While everything is working great. Ideally we would like to make sure this DNS service will stick around for a while.
So far they offer:
DNS Round Robin
Advanced DNS record editing
Custom TTL times