Cross-platform UPS shutdown?

I've got an APS SmartUPS 1000, which is powering my computers (one Linux, one Windows). Currently, I'm doing nothing when the power fails: the UPS will run down and then the PCs will lose power.

Any suggestions for software that I can run on the Linux box that will trigger a remote shutdown on the Windows box? Or vice-versa?

apcupsd.

I concur. It works quite well.