Not sure how one goes about even finding out whether a currently manufactured PMP has such a capability built in, unless a person actually OWNS one.

A workaround that I used to use with iPods was loading a smart playlist created in iTunes onto the device that chose content based upon the number of plays. Problems occurred using this strategy, however. One was that this method was limiting with what can be actually edited on the device since the playlist can only be modified on the computer, then copied back over. Say that you wanted to limit the songs chosen to those files that have been played 20 or more times, but the smart playlist was originally written to allow songs that were played 10 or more times. The edit of the filter would have to take place in iTunes on the computer, then re-synced to the iPod. Or a new playlist with the updated filter would have to made within iTunes then copied over. Either way it's a pain because all the work has to be done on the computer.

Another is that when "copying" this playlist from computer to iPod, it also syncs all media with it as well. Fine if you don't care what 10+ played songs (for example) get copied over, but perhaps there were certain file types that worked fine at home but you might night want on your portable, say due to file size or a specific filetype. At home I listen to a lot of WAV files, but many times don't want those on a limited cap portable, so care has to take place in creating such a smart playlist based upon using play count metadata prior to syncing.