Not in the jeep, but I've done it in my plow trucks ('73 Jimmy & '91 Bronco)
Depending on why you need dual batteries, there are a couple different ways to wire them up.
Personally, I hook them up in parallel, with an isolation solenoid between them so they're separated when the key is off.
Looks like you can get a dual battery tray from multiple aftermarket vendors.
If you decide to do this, be sure to keep us posted.