Actually, it could be VERY useful. For example, a liquid filled lens could change its shape/focal length.
If the fluid releases electricity proportional to the pressure exerted— then it could work like a piston.
(I don’t know why you would want to do this. But if the pizoelectric fluid will emit electricity with steady pressure rather than alternating pressure and release—then you could just use constant gravity and a rock to generate the pressure on the fluid.
Of course it would be useful. But there won’t be any electricity available to make it useful.