We did the autocom route and it worked ok but just another thing that could give up the ghost. Can also cause panic and confusion if you only hear half the message.

Our xr250's also came with lights permamently on so we fitted on/off switches.

What we eventually found most effective was that my wife simple stopped when she wanted to. I would notice sooner than later that she wasn't there anymore and come back to find her.

Small flag
 

How about carrying and waving a small flag? Can agree on two or three signals.

Jim