We present the design and preliminary simulated performance of a highly scalable TOF-PET detector concept. The UTOFPET project aims at the development of a TOF-PET detector module, with beyond-state-of-the-art performance, that is designed to be well suited for various applications, from brain-dedicated to total-body PET. The UTOFPET detector is based on a continuous scintillator crystal read out by 256 SiPMs, arranged in a 16 × 16 matrix whose outputs are processed by a stack of local processing and data acquisition boards. Initial simulations indicate the feasibility of on-board real-time position and time estimation with a spatial resolution below 0.5 mm FWHM for the whole detector.