Oh, you're talking about signal lines, I was thinking about power, implementing my safety measures are still a good idea but the overvoltage protection really needs to be designed in to the system.
Protecting signal lines agains 180V spikes isn't that difficult, take a PIC for example, just connect each IO pin to +V and 0V via a diode and connect a 1M resistor in series with the external device. The procedure is similar for op-amps, connect the pins to +V 0V and -V via diodes and make sure the input resistors are high enough to prevent high currents from flowing throught them.
If the overvoltage protection is an afterthought, then zeners, MOVs, SCR crowbars and gas discharge tubes are your friends but they're not fool proof and if they gat damaged you might not know they've blown, it's best to check them as often as you can.