We need a wireless microphone solution where we are able to monitor the on/off status of user's microphone.
We are only needing a single channel, so the UA888 seems like overkill.
It looks like the UA888 gets squelch activity from the receiver via an RS-232 interface. Do the wireless receivers have a dedicated pinout for squelch status, like >10v means squelch broken and <10v means squelch unbroken?
You did not specified the model number of your system. Assuming that you have the UHF system, Shure offered the UA111 which interfaces with only one U4S or U4D receiver. It uses the same software as the UA888.
The connector in the back of the receiver is not RS232. The UA111 converts all the different signals present in the back of the receiver to RS232 codes.