On call shifts are a waste of time. You don't really get any orders, you end up sitting around wasting your time! Better to have Scheduled shifts.
Don't do On Calls. It is stupid, they expect you to sit there in your car waiting and the so called system barely generates orders to you. Waste of time.
You have to be in your zone, but my house is in my zone. I wouldn't bother with on call, you will get about 1 order per 1.5 hours, so basically you don't have enough time to relax at home but also aren't making more than $30 per shift. Worst of both worlds.
As long as you are able to drop everything and go when you are matched with an order, you can do whatever you like during an on call shift. You wont get any matches if you are not in your zone.