Cell Phone Signal Booster

My brother and I got my parents a Verizon cell phone for Christmas, but the phone has poor reception in their house. The reception is fine outside the house or inside near their big windows. The problem appears to be signal strength inside the house. So...

Can anyone recommend a device to boost the signal strength? I don't need a specific device. I can look up the details later. I just need to know if signal boosters really work. Here is an example of a device I'm looking at: 9625 Wireless Extender - Repeater System. It is available at smarthome.com for 1900 Mhz phones. Another model is available for 850 Mhz phones. Do these types of devices really work?

Thanks,
Scott