The PoIC stack concept can be implemented in software. An existing calendar/to do/notes app already is a database with time and date stamp (tags may not be present). All one would have to do is add a 3x5 card design interface and display a stack of cards in the same way as this photo: http://www.flickr.com/photos/hawkexpress/189967397/in/set-72157594200490122/

I'd love to see an interface like that in software. Also, implementing this in software allows one to search.