so an idea about physical payment token arised on irc,
main points * keypad for pc independent pin code entry * cheap 7seg screen for payment sum confirming * prom for program memory(possibly a protected ucontroller) to guarantee uninfected device side software * eeprom for wallet.dat(encrypted with decryption key only on prom with read disable keys switched on prom) * some communications with pc to get payment data for user to confirm and to sysnc wallets
benifits * protection against infected pc, private keys never leave the device * over the counter payment