We propose to realize of a new class of interferometers based on entangled states of atomic Bose-Einstein condensates. These will have sensitivities beyond the shot-noise limit, potentially approaching the ultimate Heisenberg limit dictated by quantum mechanics. Our goal is to achieve an optimal control of the entanglement by means of novel experimental and theoretical tools to fully exploit its capabilities in precision measurements of time, forces and accelerations. A successful completion of this project will disclose a new generation of quantum-enhanced sensors for applications and fundamental physics, and also lead to a better control and exploitation of quantum entanglement for ICT purposes.