Attach LEAP to chest, what to take care of?

Hi, there aren't any inherent issues with moving the device relative to the background. In fact, the hardware and software are optimized to ignore the background and only look at the hands and tools within the field of view. There are exceptions to this where the tracking can degrade, such as if the sun is shining directly into the device or other harsh conditions that saturate the sensor with unexpected infrared light. Similarly the current version of the software may get a little confused if clothing or reflective objects are in view.

For your use case, another thing to keep in mind that the orientation of the hands relative to the device is often a more important factor in determining the reliability of the tracking data. For example, pointing your hands directly toward or away from the device will result in jumpy tracking in the current version of the software. However, this will be substantially improved in the coming weeks in order to allow hands and tools to be at much more extreme angles relative to the device. At that time your use case should be able to be implemented more easily and reliably. Nonetheless I'm glad to hear that you're already seeing good results with what you want to achieve.