This app was mentioned in 1 comment, with an average of 2.00 upvotes
Cannot comment on the data storage of that particular instrument.
I can answer your last question though. We have connected our Nikon NIVOs (via bluetooth) to an android phone using this software. It doesn't appear that the DTM821 has bluetooth available, so you would need a USB OTG adapter for your phone and USB to serial adapter for the data collecter.