I have been using the Pomodoro technique through the app Focus 10, and the results have been good. It allows you to chunk your work in a way that is conducive to finding your flow. I've been using it casually, meaning I'm not strictly adhering to the Pomodoro sequence and rulesets (I have never "abandoned a Pomodoro" because an unexpected distraction has arisen).
Whenever I'm confronted with a loading screen or some other technical hitch that requires waiting, I almost instinctually load Twitter and see what's doing. This is true whether I'm on the Pomodoro clock or not. But when I am on the clock, reading twitter even for a minute completely murders my flow, much more than the technical setback does (I imagine this is primarily because social media is depressing as hell). Which is why I usually pair my Focus 10 with Block Site. This second layer of flow-protection prevents my Twitter muscle memory from taking my focus away from work, even for a minute.
For my SmartPhone I have a similar system using a "Minimalistic Material Timer" and ClearLock. But it's cumbersome to have to sync two apps at the same time.
I think creating an app that integrates these two functions into a single app would be well received. During a Pomodoro "work sequence", user-selected apps will be locked from use. During the "break sequence", they are unlocked. As a web-browser plug-in it would work the same way, but blocking websites instead of apps.
I'm going to start designing this concept and see where it goes.