Track linear position (1 axis) wireless

[Viktor]

Hi Guys,

I have a project where I need to detect the linear movement in 1 axis of a cylindrical tool 15cm (length) and 8mm diameter moving inside a pipe that is 15 mm dia. How do I detect the linear position movement of the cylindrical tool inside the pipe ? (preferably wireless if possible).

What sensors would you guys recommend in this case? 

Thanks.