First, both plants are self-fertile, they pollinate themselves for the most part, so cross-pollination is minimal and most seed savers don't worry about it with those crops. And if you are growing hybrid varieties then seed saving is rather pointless anyway.

Second there is a great FAQ here about how to insure NO cross-pollination if you plan to save seeds.

It is important to learn which vegetables self-pollinate and which require insect or manual intervention.

The search will pull up many discussions about this question for you and I have linked one below.

Dave

Here is a link that might be useful: How to prevent cross-pollination

The easiest way is to put a small bag made of something bees can't get into around a flower cluster before it opens and take it off when small fruit form, making sure to mark that cluster for saving. This applies to peppers and tomatoes but not squash and melons of course.

Many seed savers save tomato seed without bagging but peppers will more readily cross with the aid of bees. 50-150 feet between pepper varieties would be necessary for purity if you did not bag.

As for bags, any mesh fabric like row cover or those little tie top jewelry bags or even waxed paper will work. If you wiggle the cluster in the bag it helps distribute pollen.

OK thanks little_minnie and digdirt!
It helped a lot!

The thing to remember is that you do not have to do bagging/protection all season long. Just try few buds early on, until they set fruits. Then remove the bag(whatever) and tag those fruits. You don't care what happens with the rest to come. One or two tomato or pepper can provide you more than enough seeds.

JMO