When a migrant rescue non-profit asked Nik Zemke if he could design an app to pinpoint ships in distress in the Mediterranean, the German web developer headed to a hackers’ convention to look for like-minded volunteers.

He found help among the hordes of tech hobbyists huddled over their laptops at the Chaos Computer Club’s annual gathering in the northern city of Hamburg – a mecca for hackers and activists intent on using their coding skills for social good.