How to deal with people looking at their mobile phone during my presentation?
My attitude to life is to spare my mental capacities to things I can affect and change. Yes, it is annoying to see people at a workshop not paying attention. No, there is nothing I can do in the moment that would (i) change their behavior, while (ii) not make me look petty.

So, disengage from these feelings. Focus on those members of your audience who pay attention and interact with you. Make a resolution to have a great first slide for your next talk that may sway one of the two (or maybe both!) to get pulled into the talk. These are the things I can affect.