For easy-to-use OSX automation I'm a big fan of Hazel: http://www.noodlesoft.com/hazel.php
I bet you could set up something similar in it.
This is a pretty good idea. Add the ability to tag a file/files with TTL from the CLI as well.
Source code: https://github.com/tdlm/os-x-self-destruct
This is awesome. I've been waiting for Yosemite's JS Automation so I can do some similar things with my downloads (Moving into folders based on tags, etc.) so this is going to be fun to play around with.
It mentions it uses srm, is that any use with an SSD with wear levelling etc?
Interesting idea, can anyone give me ideas for specific use cases in everyday use?
Is there no at(1) on OSX?
If this was based on atime instead of mtime, and was coupled with Time Machine backups, it'd actually make an interesting form of Hierarchical Storage Management. Files would "expire" from your local disk, but still be restorable.
On a tangent, that's really what I (and I think most people) want from HSM—not "files canonically being on slow media but being cached on faster media", but rather "files canonically being on small/fast media, and then migrating to slower media when you stop caring about them, as if a garbage-collection pass had occurred, leaving your disk with more space." Basically, HSM should do automatically what people do manually when they e.g. burn files to optical disks to clear up space.