Lots of IT jobs that deal with critical infrastructure have on-call duties.

Try working for some IT firm that supports healthcare, utility, defense, or what not, and I can assure you that there's rotation duty where you need to be on-call within xx minutes, 24/7.

During college I was interning for IT firm that provided networking for local hospitals, and they had the same rotation. My friend who got me the gig, worked there FT, and he basically had to forego social activities every 3 or 4 week, because he'd be on call 24/7.