A small hardwired inverter to run satellite, charge laptops, etc.
A simple cheap ebay Amp-hour meter, like a real gas gauge for your batteries.
A folding tilting or rocking chair to sit up by the bed and watch TV.
Those are my projects at the moment. We do camp off-grid quite a bit, so the first three are very worthwhile. I found the romex wire that feeds the outlets by the TV and bunk bed, so I'm separating it from the 120v circuit, and will run it off the inverter at all times. Well, whenever the battery switch is on. I'll do write ups here for all of the mods.
2014 Sunseeker 2300 Chevy