Just a feature suggestion, no idea if it would be possible:

multiple worker tracking. Akin to how you have your vardiff +# at the end of the address, maybe a -1,-2,-3 to keep track of mulitple workers to make sure that each one is mining properly? Of course that would require doing multiple synching/lookups on the same page, I don't know if your servers can handle that kind of load or what kind of load that would require for the active refresh to continue to work in that fashion.