I'm experimenting with developing a series of mp3s that guide you through practicing a particular technique (vibrato, spiccato, finger action, etc.). It is intended for those who may need help being consistent and organized with their practice routine. The idea is not to teach, but provide a bit of structure and simplicity (just hit the spacebar and start practicing!) in order to make the most of a practice session.
I've uploaded a beta version of "Vibrato I" here:
http://soundcloud.com/vaultnyc/violin-trainer-vibrato-i-beta

If you have some time and can listen and/or download it and give me some feedback on any part of this I would appreciate it very much. Do you think this would be useful to you? What do you like about it? What don't you like about it?

There is much more I can say about this concept. Here are a few thoughts: Tracks put into playlists can become powerful practice routines or warmups. Statistics built in to mp3 playback software can track progress (number of plays, dates, etc.). Tracks are portable (iPod/mp3 player) and work with one earbud in ear. Practice intervals and rest periods will be derived from neuroscience data on learning to optimize results. Tracks with guided Alexander Technique sessions could help tension issues. All in all, a lot of guidance at your fingertips.

Playlist image:
http://www.flickr.com/photos/8791696@N06/8232565061/in/photostream