Walkie-talkies

• Walkie-talkies can be used alongside a huge range of group games (such as capture the flag), as they're fun to use and can be handy for planning team tactics. Alternatively, with small groups, assign one player as the "target," and the other players as the "agents." The agents' task is to covertly follow the target around and report his movements over the walkie-talkie; the target wins the game by escaping from their surveillance for at least 10 minutes.
  
  

Motion Sensors

• Purchase several motion sensors and arrange them around a room at various angles. In the middle of the room, place the "diamonds" (represented by a necklace or other jewelry) on a chair's surface. The players take turns navigating around the motion sensors, trying to acquire the "diamonds" without setting off the alarm. The more motion sensors you use, the harder this game becomes.
  
  

Lie detectors

• Several products exist that aim to predict whether the participant is lying, and some will give them a little electric shock if it thinks they're being deceitful. This can be a great basis for a game, as players can compete to be the most "honest," by answering the most number of (embarrassing) questions truthfully.
  
  

Listening devices

• In this game, two players use long-range listening devices to eavesdrop on the other players. While doing this, they note all information they hear about conversation topics and the specifics of what's being said. The two players then come back to the party, and the person whose notes are the most accurate is considered the winner.