T will say one of the following (or a variation of them):

"We need to get out of here now."
"I'll let you go."
"Looks like our time's up."
"Do you have anything else you want to say before we go?"

I would not do well with a timer! Especially if it actually just cut things off. With my T, it's not uncommon to go over our hour...We never just end, we always wrap things up first.