For the amazing price of $0/£0, you can get Zombie Highway
I got this on my iPad and I've so far lost 5 hours of sleep over it. Put it down this morning at 2am when I couldn't keep my eyes open, then at it again today. Consider yourself warned!
I do feel, however, that it is my duty to share this precious "training simulation" to all fellow SimHQ-ers in preparation for the zombie apocalypse