I have researched the same issue ie. Printing from an Ipad to a small mobile printer
The Ipad can only print by WI-FI to a e enabled printer. It cant print by Bluetooth
The only suitable mobile printer is is HP OfficeJet 100 Which prints by Bluetooth .
There is a workaround and you will find an excellent Tutoral on google using the How to print to a mobile printer
You use a DC to AC Power invertor 150 Watts that you can plug into a cigeratte lighter
You use a cheap WI-FI Router that picks up the signel from your Ipad and directs it to your ePrinter 230V. Both are pluged into the power invertor
There is some important seting up the WI-FI Router and Printer on your PC first
The power invertor I use Auto shuts off when the battery DC Voltage falls below 10V DC, I have it set up in back of a van and it really works I print of hard copy receipts to customers
I hope Apple are having look at this Issue Afterall they are touting the Ipad as a mobile business platform. Judging by the forams there are a lot of Business people out there disappointed to put it mildly. Printing by Bluetooth would sort out this Issue.