The $1 Budget: Adapt, Test and Bubble!
Three more items found for a crisp dollar may help you along your filmmaking journey. This month I look at some 3-prong to 2-prong outlet adapters, a battery tester and a magnetic level. Not what you were looking for? Leave me a comment about your $1 find and if I use it on the show I'll give you credit and send whatever traffic I can muster to your YouTube channel or website.
Cross Check Level
7 Function Multimeter
Regarding using an iPhone, I agree with Michael; in a pinch they will work. Don't expect too much, but they do give a decent spread.
I shot a DIY project for my cousin last year and we had to illuminate a room with iPhones. If you can imagine, a three-point setup with human light stands. I can give you a link to the video if you want to check it out.