The advantages are that it is open source (if you want it to do something extra, just change the code yourself), a smartphone/tablet provides a much richer user interface and more processing power than the simple devices being sold as darkroom timers. They can become significantly smarter.
Originally Posted by Moopheus
For example, you could use the built-in camera to look at the enlarger output on the baseboard and from that, choose a printing grade and some dodge/burn suggestions (illustrated on the screen!) that will result in a fairly well-balanced print. The possibilities are hugely expanded.