I don't know where you are on the programming spectrum, but if you get into ProntoScript, look into TouchControl
. While it's a very different programming style. You can recreate your Pronto on an iPhone (less the hard buttons). Pretty much, the limit is your imagination and you might be able reuse bits and pieces of your ProntoScript code. This is not, however, the "click and go" sort of setup style of a Harmony.
By the way, Harmony has stopped manufacturing, but there are probably still some units in the pipeline, If you haven't looked at their software in a few years, it has improved greatly from the original and you might be able to live with it, but it's not Pronto.