I don't believe that the specs for NTAG203 allow for any more data - although I'm far from an expert so could be wrong here. According to http://www.gototags.com/docs/display/NFC/NFC+Chip+Types (they sell tags, so take any information as a sales spiel) the Type IV tags hold huge amounts of data - they're also about $3-4 each. Expensive, but not too bad if you're only after a few. No idea whether they're readable by the S4, but on a forum elsewhere I saw someone recommending Type IV tags (the conversation was specific to the S4), so it's possible. Personally, until I see someone say that they've used specific tags successfully with the S4, I'll be wary of getting them
We have a ACR 1252u NFC card reader. We want to read/write NFC cards on Android with this device. The problem is that this device is not seen as a NFC device but as a USB device instead. Therefore native Android NFC can not be used. Currently we are able to detect the device and to trigger an event by adding or removing a card. But we are neither able to read nor to write a card. In the documentation we found some HEX codes that are transmitted to the device, but we did not figure out how they work in order to read/write cards. Also on the net we found some example codes using other ACR devices but obviously they are not compatible to our one.