Block Sensor is a rare item in Mario Party DS, only appearing after the 15th turn of a game. Resembling a satellite dish, it allows players to detect hidden blocks that are scattered across the board.
When used, the player is alerted that there is a hidden block detected. After the player rolls a standard Dice Block, he or she is awarded with a hidden block on the space the player landed on, regardless of the space. The effects of the space occur and game proceeds from there.
The Block Sensor only detect blocks, and will not determine the contents of the box. These boxes will have coins, a Star, or even a Ztar.
A Block Sensor can be obtained by using a Grab Bag or buying it at an Item Shop, at a cost of 20 coins.