I just bought a Jolly Logic Chute Release after seeing it work for my rocketry friends. I used it today for a perfect flight with the chute opening at 300 feet, keeping the rocket from drifting in the wind. It is a small electronic device that releases your parachute at the altitude you pre-specify.
The device is a highly accurate atmospheric pressure sensor that releases a pin holding the rubber band, wrapped around your chute, at the specific altitude of 100, 200, 300, 400, 500, 600, 700, 800, 900 or 1000 feet.
It is easily recharged with a USB charging cord which is supplied along with the release pins, rubber bands and tethers (so your chute release stays attached to your rocket). It is made of strong polycarbonate plastic to stand up to ejection charges and impacts.