Project cost: less than $10 ($6 for the water bottle and fleece for a cover is cheap. I used a piece of fleece I had leftover from another project, so it was $0 for me.)
I love my heating pad. It goes up to 11, it's huge, helps with a variety of maladies, and it won't work in the Vanagon! :(
Road trips mean you have to find solutions to all sorts of challenges and become some sort of clairvoyant, trying to think through all the potential issues you could encounter. I've been systematically going through the items we use and trying to find van-friendly alternatives. This one definitely needed attention. I mean, a sore back, cramps... how are you supposed to make that feel better if you can't get heat to it?
I toodled around through some Google searches and didn't really find anything that didn't involve a mircowave or just a regular heating pad - obviously neither will work for us. Then I remembered hot water bottles! Genius. We can boil water (or just use the hot water out of the tap now that my fabulous husband has installed a hot water heater) and voila! pain relief.
Not wanting to encounter an unexpected problem when I needed soothing heat the most out on the road, I tested this sucker out. It stays pretty hot for a long time and didn't leak. The biggest problem, THE SMELL! It reeks of chemicals (off-gassing rubber, I think) and I am not too happy about that. I put it in the dishwasher - it helped a little. I have also left it outside and in the open air on the table for a couple of weeks. I think it's finally wearing off. Otherwise, perfect solution for less than $6. We got ours here.
Making a cover for it took all of about 8 seconds... which shows in the quality of the end product. I am not very good at sewing. It's something I have never really had the patience for. I suggest spending 10 seconds on sewing this simple bag so that yours is square and the hems will actually hold. I don't care, so I left it the way it was.