Just came across these:
Lock Alarm - Cable Lock with 120dB Tamper Siren
A group could carry one of these, and lock up all the rear wheels at once. The alarm goes off if the cable is cut.
It comes in several cable lengths
8 ft - http://www.mcmelectronics.com/product/LOCK-ALARM-6796-/82-19810
15 ft - http://www.mcmelectronics.com/product/82-19815
30 ft - http://www.mcmelectronics.com/product/LOCK-ALARM-6798-/82-19835
Lock Alarm - Cable Lock with 120dB Tamper Siren
A group could carry one of these, and lock up all the rear wheels at once. The alarm goes off if the cable is cut.
It comes in several cable lengths
8 ft - http://www.mcmelectronics.com/product/LOCK-ALARM-6796-/82-19810
15 ft - http://www.mcmelectronics.com/product/82-19815
30 ft - http://www.mcmelectronics.com/product/LOCK-ALARM-6798-/82-19835