I have been attempting to research this for years, checking and being disappointed by many trainers. I’ve had good luck in the past maintaining my cardio with a magnetic clutch trainer but other things take priority. If I only had a trainer that would audibly alert me if my RPMs go outside the target rate for the program I’m running I could do other things while I’m exercising instead of staring at the display. I assumed this would be a more or less common feature but I cannot find it. This forum seems the most informed on crosstrainers so if someone could tell me what product line or lines have this feature (preferably one that has for a while so I could pick up a used machine) I would appreciate it greatly! Thanks in advance!
usually this is done at other levels.
You can set alarms on the watch to let you know if you are out of certain rates (HR, Pace, speed, cadence, etc). Or at least you can do on garmin watches.
I have a motoactv but I know for a fact it doesn’t have a speaker. It hadn’t occurred to me that something like a fitbit might interface with a modern crosstrainer to give me an audible indicator.
YOU HAVE WHAT!? 
DUDE! You still rocking that watch? massive KUDOS to you!
It is IMO the first truly smart watch. I would tell anyone who would listen that mostly everything we have now on garmin we had on that motoactv back in 2011.
I wish mine was working, but it died due to the major defect it had: it was absolutely not water resistant!
Motorola was into something, it sadly gave up before they even started.
Yeah not having a speaker is a major issue for sure.
Maybe is time to get something slightly more modern? 
I mean, if there’s a sub-$100 smart watch that connects to trainers that are a few years old and available on the second hand market and delivers audible indicators then I’d buy one. This just hadn’t even occurred to me
Not sure about 100 new. But certainly you can get them used. I would search eBay.