I'm looking for a transmitter that when activated (say by a push of a button) would signal someone no more than 100' away via vibration much like a cell phone on vibe. Perhaps the receiver could be operated by something small like a "button style" battery.
The vibration is the easy part, all you need is a motor with an off-center weight attached to the shaft. The rest is just a simple transmitter/reciever circuit that can be picked up fairly cheaply
It seems that 50% of the restaurants here have pagers that do just what you describe. Customer is given the receiver and when their table or order is ready the device vibrates and flashes. I've never seen a project for one but doesn't seem all that difficult.
you can buy the 433mhz transmitter and receiver in kit form at qkits.com (although theyre out right now) or at elexp.com (they're in stock). They're very cheap, like $7 a piece.