security:
 - check that we are on the longest chain after a reorg
 - check SSL cerfificates of servers


wallet, transactions : 
 - dust sweeping
 - transactions with multiple outputs
 - BIP 32 


code improvements:
 - qrcode and bmp patches are on github (they are incompatible with android)


classic gui : 
 - in POS mode, request amount in USD, convert to BTC


android: 
 - kivy-based gui


protocol:
 - add client authentication, to make paying servers possible