What do you want to monitor, AC power fail and battery voltage? You could use arduino and a voltage divider and just wire it in. You can also plug a relay into a wall wart (plugged into the wall, not the UPS) and use that as an AC fail alarm point. When the relay gets power the value is 1 and when it loses power the relay returns to off and value is 0. Or vise versa if you connect it inverse. I personally like to make my alarm points normally closed, that way if something happens to the wiring it will cause an alarm.
You could measure current using a shunt and op amp too, I have not done this myself yet though but been looking into it as the cheap ass panel meter I bought is garbage and does not display the correct values. In my case I'm monitoring a large battery bank though but would work the same for a simple UPS.
For the wireless you could either have the arduino connected to a small wifi capable computer (like a raspberry pi with wifi dongle) or maybe use some kind of wifi or xbee shield. (not familiar myself with how they work - the rpi way would be easier imo)
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