Programable Vibrating Motor

A vibrating pager might be a good starting point for adapting to your app.

Looking for something small enough to fit on the back of a bracelet

Possibly the motor used to make pagers.

Or, cell phones. They are rather small. Then all you have to do is have someone call you every 1/2 hour.

I think you may be trying to be a little too specific. Any small motor can be made into a vibrating motor with a small off centered weight attached to the shaft.

These look promising. http://www.vibratormotor.com/guide-table.htm

Use a piezoelectric vibrator.

Piezoelectric Vibrator | Products & Suppliers on GlobalSpec

Get a used pager with vibrate. They have a small 1.5 volt motor with an off center weight on it - this makes the vibration.

They buy a small timer kit from Ramsey electronics and make an interval timer to run it as you wish. The vibrator motors can be bought as a spare part as well.

buy one here

Here's a useful place to choose from a variety of vibrator motors at low cost:

http://www.surplustraders.net/a/0185.shtml

Mark Bingham
Relativity PL

Thanks! Looks like a good place to begin!

Tear apart an old cell phone.

Don't know if you get these in the States, but you can get Oral-B_pulsar toothbrushes for about £3 ($5) over here. They are almost indistinguishable from a normal unpowered toothbrush but the handle is just fat enough to hold an AAA battery.