Yep. Origin of probabilities and their application to the multiverse is a short argument that says that there is quantum uncertainty in the firing times of neurons on the order of 1 ms, and that accounts for most of the uncertainty of a coin toss.

Someone brought up Dynamical Bias in the Coin Toss, which has a more serious analysis of coin tossing and would provide a better answer to the question of "How sensitive is the outcome of a coin toss to the motion of the thumb?" I haven't read it.