This paper proposes a method for depth estimation in video sequences acquired by a monocular camera mounted on a mobile platform. The proposed algorithm is able to estimate in real time the relative distances of the objects in the field of view exploiting the parallax effect, provided the platform movement complies with a few constraints. The developed system is designed to operate at the input pixel cadence and is thus applicable to any video resolution. The final architecture, using operators no more complex than an adder and a memory that is just a fraction of a frame memory, can be realized in a low-cost FPGA.