  We present in this article a novel Lagrangian measurement technique: an
instrumented particle which continuously transmits the force/acceleration
acting on it as it is advected in a flow. We develop signal processing methods
to extract information on the flow from the acceleration signal transmitted by
the particle. Notably, we are able to characterize the force acting on the
particle and to identify the presence of a permanent large-scale vortex
structure. Our technique provides a fast, robust and efficient tool to
characterize flows, and it is particularly suited to obtain Lagrangian
statistics along long trajectories or in cases where optical measurement
techniques are not or hardly applicable.
