Probably the most dangerous tool in a shop is the table saw. SawStop is really the only truly foolproof method to prevent injury. Unfortunately, they are not licensing their patent (even though they tried to initially), and they have shut down several other companies who have come out with similar mechanisms (at least Bosch).

The downside to this is that the cost of safety is relatively high ($2000+), and there is no way to retrofit high-quality used saws from the used market ($500+)