According to the product description, the flex/bend sensor was popularized by Nintendo as a gaming interface for gloves. As the principal motion that our body makes is bending, the bend sensor offers many possibilities in which a device responds to body movements.
This sensor measures the proximity of objects. Despite its simplicity, it would be very useful for a number of projects – especially those involving robots or other machines that require methods of collision prevention.
I was mostly drawn to this because it was dubbed “the poor man’s accelerometer” (and it’s only $2.00). Although it is not as powerful as a “rich man’s accelerometer”, its size makes it very convenient for small projects that require basic orientation/motion detection.