  Hole-spin qubits in semiconductors represent a mature platform for quantum
technological applications. Here we consider their use as quantum sensors, and
specifically for inferring the presence and estimating the distance from the
qubit of a remote charge. Different approaches are considered - based on the
use of single or double quantum dots, ground and out-of-equilibrium states,
Rabi and Ramsey measurements - and comparatively analyzed by means of the
discrimination probability, and of the classical and quantum Fisher
information. Detailed quantitative aspects result from the multiband character
of the hole states, which we account for by means of the Luttinger-Kohn
Hamiltonian. Furthermore, general conclusions can be drawn on the relative
efficiency of the above options, and analytical expressions are derived for the
Fisher information of a generic qubit within the Rabi and Ramsey schemes.
