I would like to see a Data Matrix Reader. I currently use a Quartz Composer plugin created by Dieter Wimberger who graciously made his source code publicly available under a BSD style license. There may even be interest in other types of barcodes and perhaps QR codes being read as well at some point.
(Mockup by Team Vuo.)
For the proposed node, we'd plan to use zxing, which supports DataMatrix, QR Codes, UPC, Code 128, and several other barcode formats. The node can detect multiple barcodes in a single image — it outputs a list of text items, or an empty list if no barcodes were found.