Yeah. There is a part of the pomodoro technique where you capture extraneous thoughts to then offload it from your mind. You look over that stuff during the 5 minute period to see if it was really as urgent as you thought it was. It is structurally similar to the Noting practice from insight/vipassana. My own experience with both pomodoro and meditation is that the mind will try to play tricks on you to get you to avoid doing unpleasant things by bringing up something that is more pleasant. That capture technique is a good way to manage that kind of stuff.

I used to use a notebook (as described in the original Pomodoro pdf) and now I just use org-mode in Spacemacs.

I usually spend the 5 minute break time meditating or working through some empty hand forms. When I do all of that, it has been very effective for marathoning coding without using external stimulants like caffeine.

Added bonus: using the Wim Hof (Iceman) breathing method and cold shower during the 30 minute break to oxygenate the body and brain. I usually feel like I just woke up fresh from a good night sleep, ready to go for another series of pomodoro sessions.

Lastly: I am working (on and off) on taking the principles and View of classical (medieval) non-dual Shaiva Tantra and applying it to writing code. There are a lot of good insights there that are applicable to working in a modern job, and it goes beyond mindfulness. Tantra, in both it's Shaiva and later Buddhist/Vajrayana versions have practices involving creating art, form, aesthetics, and beauty that is often missing from the attitudes towards work and productivity here in America. Tantra requires a solid foundation in mindfulness (among other things).

If you have sox installed, simply

      while true; do sleep 1800; play -n synth 0.15 sine 800; done

Visual version, avoids disturbing coworkers

  brew install screenbrightness
  while true; do sleep 1800; brightness 0; sleep 0.1; brightness 1; done

Or, in powershell (sans sox),

     while($true){(New-Object Media.SoundPlayer "C:\YourPreferredSound.wav").Play(); sleep 1800;}

I'm using the Single Hit Tibetan singing bowl from: http://www.sound-effects-hunter.com/tibetan-bowl-sound/

Does this help you mentally? What changes have you seen since starting this 'mindfulness' practice?

I'm hesitant to say anything about mental effects, since I'm far from able to objectively measure such things, especially since I haven't been keeping any kind of measurements or records. But it certainly keeps me from slouching quite as much.

I made a free macOS app based on this technique: https://itunes.apple.com/us/app/zentime/id1089216789?mt=12

This would be a killer Apple Watch app.

Who needs an Apple watch? Timex digital watches have been dinging every 60 minutes for decades.

Agree, especially with just a gentle vibrating reminder that turned itself off after a second. I've tried a few of these, and the problem they all suffer is obnoxiously intrusive notifications. It's not an alarm clock, if I miss one it's fine.

Agree, it's more about noticing whether or not you're focused than it is being forced into a workflow.

Doesn't "Breathe" do this?

http://www.macrumors.com/2016/06/13/apple-breathe-app-for-ap...

This app helps with that: http://www.42burnside.com/mindfulmynah/

Doesn't it distract you when you are in deep work?

It usually helps me refocus. A quiet alarm isn't enough for me to lose track of what I'm doing, but working myself to exhaustion usually does.

Yes, but only slightly and not enough to prevent refocusing quickly. In the long run it helps with overall mental stamina. It helps keep me from distracting myself with other things which take longer to come back to a problem from.

I do that too, sometimes even more frequent.

You really don't need an app for that, there are tons of videos on YT serving exactly this purpose:

https://www.youtube.com/watch?v=cb49mTBTFR8

This is excellent advice, being mindful is one of the best things we can do, especially with regard to stress and worry and posture as you noted.