I recently stumbled across an interesting little programme: http://slowmovideo.granjow.net/. It enables the creation of slow-mo videos from clips that have been created with normal speed/frame rate without some of the downsides of just reducing the frame rate.
The software is part of a BA in Computer Science at the ETH Zürich (Switzerland), and the underlying thesis (describing the underlying concepts and algorithms) is also available from the website. It’s only available for Linux, but the results look very interesting, even though the UI (standalone or integrated into other programmes) needs some rethinking. It also uses Qt and ffmpeg.
As mentioned above, nothing urgent, but nice to have.