But what do you do to complete these purchases like in a cafe or something, you use a tablet/smartphone to do the BTC transaction?
Just WIFI, a somewhat busy cafe and some trust they won't kill you/rob you/give fake money/too little. Almost every cafe has WIFI now. In the Netherlands you don't have to be afraid for cops getting you this way, they are restricted by law.
There is some risk. You will have a problem if you travel around the city with a lot of money.