Does anybody suggest a mobile printer able to print receipt with a good SDK to interface wireless an iOS application adhoc developed ? The printer should be small and should
Unfortunately iOS5 does not support Bluetooth printing.
http://support.apple.com/kb/ht3647
Have you considered VPN via WEP to a network printer?
Alternatively some printers can be set up with their own email address. PDF attachments can be sent via this address to be printed. These emails can be sent encrypted.
I know that this isn't the IDEAL answer, but it is likely to work for the time being until iOS is properly updated.