This might not be the best solution, nor the most elegant one around, but I managed to accomplish my needs with the use of a Triggerlinc connected to two foils of aluminum paper (10x4 in. ea.), backed by duck tape. Sandwiched between both foils, I inserted a 1/8" piece of the exact same size of hard upholstery foam, with 5 holes the size of a quarter. The whole thing fits under the seat cushion and reports an 'open' state until someone sits and compresses the 'device', promoting contact between the two layers of foil separated by the foam and closing the circuit... Believe it or not, it works perfectly each and every time...