http://www.tetrixrobotics.com/TETRIX_Chain_Breaker_Tool
We got one of these last year for our FTC teams. They work pretty well, but the pin broke when one of our students didn't use it properly (i.e. the chain wasn't seated in the tool and they torqued it down onto a chain sideplate...) Luckily, we were able to manufacture our own with a hardened dowel.
We liked the design so well, we actually designed and manufactured our own #35 chain version.