I'm an hourly employee, and I'm on-call on Saturdays and on certain holidays when the office is open for Customer Service. Mainly, I just carry a company celphone around, and should be in-town in case I have to come in.
In ways of compensation, I get 2-hours of "stand-by" time, but I have to be available for the 6-8 hours the office is open. If I have to be called in, I get a minimum 4-hour call-in time. It can be at over-time or regular depending on if I put in a 40-hour work week.
Out of the 2 years I've worked here, I've never had to go into the office, and I've gotten just a handful of calls which were quick and easy to fix over the phone or by vpn'ing from home. No complaints and it's like getting 4 extra hours for free each pay period.