[msthomaa]

As the other comment said, PocketCast does this for podcasts, you can set it to cut the silence. Also I believe Overcast on iOS.

For audiobooks, Listen Audiobook Player on Android does the same, though for some reason I find it distracting for audiobooks.

[jessriedel]

Unfortunately, PocketCast isn't very aggressive about clipping short pauses in speech, probably because it would tend to mangle things unless done carefully. (I suspect it would require a lot more software sophistication with human speech to appreciably change the average playback speed.) It cut out less than a second over the first few minutes of a conversation I used as an example, so it essentially does nothing.

Thanks for the suggestion, though. I never tried Overcast since I'm on an android, but I suspect it's similar to Pocketcast.

I really wants something that ups the average speed to ~2.5 while maintaining intelligibility.