  We investigate the effect of Dzyaloshinskii-Moriya (DM) interactions on
torque measurements of quantum magnets with magnetization plateaux in the
context of a frustrated spin-1/2 ladder. Using extensive DMRG simulations, we
show that the DM contribution to the torque is peaked at the critical fields,
and that the total torque is non-monotonous if the DM interaction is large
enough compared to the g-tensor anisotropy. More remarkably, if the DM vectors
point in a principal direction of the g-tensor, torque measurements close to
this direction will show well defined peaks even for small DM interaction,
leading to a very sensitive way to detect the critical fields. We propose to
test this effect in the two-dimensional plateau system SrCu$_2$(BO$_3$)$_2$.
