Sammy screamer $40 motion sensor, works from your smart phone as controller. Dobermanproducts -$20 motion sensor with key pad and pull pin both are small can't weigh much. Also from Rei item# 875927 a 30" cable combo lock, retractable -2oz. designed for skis & snow boards. I bought 2 locks, 1 for the bicycle, 1 for bags, and a screamer. Not sure either will come hiking, but maybe.