Ho,
what about this:
> watch elf
you see:
You start watching the hairy, ugly elf
he sees:
The shining hero starts watching you
now stupid elf does:
sneak ; north
and even if his sneak skill would allow him to normally be unseen, due to
the 'watch' the hero gets:
The hairy, ugly elf sneaks northwards !!!
effect:
if i look at someone intently he cant just leave without me noticing
---someone---
Actually, "Listen" skill already may help you see the sneakers sneaking away.
But such an addition can be also good. As long as the watched guy gets the echo that he is being watched.
EDIT: Follow the guy. So you really are "watching"