That's certainly another way to do it.
I haven't had much luck with X10 signals passing backward out of a UPS. Did you test that when the UPS switches to battery, and then switches back, that the time isn't lost? Did you run it long enough to verify that it doesn't gain or lose time while on battery (depending on the design of the clock, the backup power sometimes is slightly off in frequency - enough to mess with clocks).
