Right now availability metrics for beta cluster are coming off a diamond collector that shells to varnish top to see 5xx rates.
I think having a simple catchpoint web check (super cheap!) hit enwiki to see if it's listening would be a good other step. In an ideal world we'd duplicate all the prod checks for beta, but in an unideal world, we could setup *some* cheap checks so we have more reliable metrics to deal with.
So I'd say, to start with, just a simple check for enwiki on betacluster's main page? Ideally we'd do one with debug=false, and then check for a string to be present in there (this is what shinken does atm).