Ever heard of a cloche ? It will raise soil temperatures and fruit temperatures in a small area, especially if you have only a few hot peppers.
Best bet is to use a 'Hot Frame' , slightly vented for larger areas .
Hot peppers need temperatures of 78-92 degrees even to germinate.
Don't forget that peppers still need pollination to set fruit , even if you have to do it by hand (small paint brush)
Consider : " Protect Vegetable Transplants With Home-Made Glass Garden Cloches " (out of glass 1 gallon jars).
http://www.funinthemaking.net/2009/04/18/apple-jug-made-into-effective-garden-cloche/
Rememeber to remove the cap on warm sunny days , or you will steam the plants when using a gallon glass jug,
or remove the cloche altogether during early mornings on sunny days .
But using cloche will allow you to raise the soil and plant temp in a small area , or a 'hot frame' for a larger group setting.
Thanks for the cloche tip! I had heard of them, but it’s nice to be reminded and hear a good description of how to use them.