This conference paper is a synthesis of several works dedicated to the optimal positioning of sensors, when one wishes to reconstruct an acoustic pressure from mea- surements performed on the boundary of a domain. In a first step, we present a generic approach to address the issue of sensor shape and location optimization, based on the well-posedness of an inverse problem. In a second step, we try to show the limits of the previous approach, by presenting an example of application to a medical imaging prob- lem, which is out of this framework and is therefore more difficult to deal with.