Am I forced to use a gyro and an accelerometer, to find a relative point in space?
Building a "power glove" or a video tracking system from scratch is definitely not a project for a beginner.

However, there are many commercial devices out there for fairly reasonable prices &mdash; mainly aimed at video game users &mdash; and your best bet would be to acquire one of them and learn how to work with it in software.

One particularly good example is the Xbox Kinect. There is a software library that allows an application developer to access most of the features and capabilities of this 3D video sensor, including sensing the position and pose (e.g., hand position) of one or more human beings.

After you have your software application working at some level, you can revisit the question of building (or buying) a better user interface for it. At that point, you'll have a much better idea of what you really need in terms of the technical details.