I've been playing around with rec-trigger. There's a special mlv_lite module in the
Experiments download page that should work on all platforms. If you configure it a certain way you can shoot single frames which is great for timelapse and animation. The way to do it is by setting the Pre-record to OFF and the Rec trigger to Half-shut:pre only.

An issue I had was that the counter shows time in minutes, seconds and tenths of seconds: MM:SS.1/10sec. so with a standard frame per second video rate you need to take a few exposures before the counter advances.

I tried changing the display so it uses a timecode like, MM:SS.FF. I thought it was pretty cool so I submitted a
pull request before testing all the possible variations of the Pre-record options. a1ex found all sorts of problems with my code so I started going further and further down the rabbit hole, changing variable names and adding menu items until I got something that might be useful. It is still quite experimental so I stuck it in the Advanced menu.

As you can see I left the time display that was adapted from the
ffmpeg time unit syntax as the default and added the option to display the counter in Timecode format or in Frames. This probably isn't SMPTE approved timecode because it is based on the record frame rate instead of the playback frame rate but it does advance every time a frame is saved and it displays pretty much the same minutes and seconds as the ffmpeg version.
If the camera is set for NTSC 30fps (actually 29.976 more or less) the frame counter goes from 00 to 29 then it advances the seconds counter. Likewise at 25fps it goes from 00 to 24 and at 24fps it goes from 00 to 23, just like timecode. This should help for those cases when you are shooting one-frame-at-a-time and need to be more accurate than 1/10sec.

If anyone wants to try it out I put a test build of the mlv_lite module which should work on all platforms in my
bitbucket download area. Look for magiclantern-mlv_lite-rec-trigger-experiment.
Feel free to post comments on the pull request:
https://bitbucket.org/hudson/magic-lantern/pull-requests/823/display-counter-in-timecode-format-mm-ssff/diff