Just as a side note, Magic is all about converting the caster's will into reality. I'm not sure that having things moving around randomly makes a lot of sense. Instead, you might have things move around in ways that the character might have wanted, assuming he actually thought about it. So, for example, if he *really* wanted that new cell phone, it might float into his backback as he turned away. Or if he started getting thirsty, he might find that a beer had mysteriously moved from the fridge to the table next to him. And so on...
(Just a thought.)