I have done a pilot project for a customer using a bluetooth barcode scanner.
Advantages over tablet camera were:
I tested with a KoamTac scanner and an iPad2. Application was not Mendix based but JavaScript/HTML5
There is a BarcodeScanner module in the appstore. This will process images of barcodes so any camera will do. In the past I have used Abbyy with Flexicapture to do barcode scanning from documents. This will produce an xml file with all the info.
From the hardware point of view I would go for the images. Then all mobile phone devices can be used. But the choice for the hardware is defined by the business process you want to make. If you need a dedicated barcode scanner most scanners have custom software that produce the data. I have no experience with such kind of scanners.
Regards,
Ronald