Quote from: jl2012 on September 23, 2013, 06:22:58 AM

Can we use the accelerometer in smartphone as entropy source (or adding it to HW wallet, costs only about 1 USD)? When generating a new address, or signing, the user is asked to shake the device for a few seconds. That should give plenty of randomness

For HW wallets, there are faster (in raw bits/s) ways to collect entropy for < 1 USD in parts and with no user interaction required. I describe some of them here: https://bitcointalk.org/index.php?topic=127587.msg1434009#msg1434009, but I am sure there are many more ways. These also have the benefit of being internal, so it is more difficult for an observer to guess the state of your entropy pool.