Cue started out as an UITableView and IBAction that played tracks from a static array I curated one late night. Today it's a combination of my own fork of Apache Cordova, a native wrapper around MPMediaItem, with an API written in Laravel all hosted on a single Linode.
Apple doesn't provide a way to bookmark specific spots in the iPod interface. However it does on iTunes (only for podcasts), but that's not helpful when you're on the go and can't remember timestamps in your head. Cue solves this problem in an elegant fashion.
Even though Cue is pretty much abandonware™ at this point, since I've moved on to SoundCloud, I still plan on making the API public and to implement new features/integrations (when I find the time, sigh).