I would also recommend a bluetooth phone and the Salling Clicker software. This is much more productive than a dedicated bluetooth clicker, since the Salling Clicker software will actually transmit the powerpoint slide notes to the phone display. This allows you to keep see your "talking points" by simply glancing down at the phone in your hand.
You don't need a cell service for this to work. Just pickup a used bluetooth phone from ebay that is compatible with Salling Clicker and you're in business. Or, if like me, your existing cell phone provider sells Bluetooth phones then you can just use that.