I recommend the http://www.rest-timer.com Great for making the workout more interesting and helps to reinvigorate you. Good stuff. and cheap too.

If they have support beams in there homes it'll be very easy, or you can get the door anchor. In takes very little time to set up, especially once you get used to it. If your customer wants to purchase their own TRX they can get the wall mount at the same time, it requires some DIY, but can make...