Sound and light can push objects. They do so by the so-called radiation force, which is exploited in technologies such as acoustic and optical tweezers, which trap and move microscopic particles. A trap, however, is a fragile object: it breaks if the medium scatters or changes in time, if the object is changed, or if our modelling is incorrect. In this talk, I will present our research on wave-momentum shaping, a way to push objects using waves that works even in inhomogeneous, time-dependent media, and does not require knowing the medium, the objects or a precise physical model of their interactions. Instead, we only need to measure the scattering of waves from electrical ports located outside of the system, and we show that we can exactly measure, predict and optimise the force exerted on any object inside of the system. This is made possible by the conservation of action and energy. We will discuss basic physical principles, as well as two experiments, in acoustics and electromagnetism. The technique may be relevant for precision biology experiments, in vitro or in vivo, and is generalisable to 3D.