My mother talks in her sleep.

We had this problem. Monitor wore out, replaced with Sony 2-monitor pkg. As many do, it has two settings-1 w constant monitoring n 2nd w voice activated control. I put monitor in our room on voice activated, n one just outside our bedroom door on constant monitoring, full blast. We also have a mattress alarm, turned down kind of low, so we don't scare mom to death. It is amplified by each monitor too very loud in our room. I am sleeping better as a result, but of course still have to get up a lot at night, so still tired, but resting much better! Good luck...

Can you hear the bed alarm without the monitor? I take it that the alarm is what you are concerned about.

i think a monitor would drive me nuts too. i think id rather position my bed close enough to see and hear her movements in bed. get a construction type family member to open up a wall for you. its only drywall..
im a guy, we make rash decisions. maybe not everybodys thing..
slash and burn. scorched earth. divide and conquor.. stuff like that..