New York-born O'Sullivan has worked as a janitor, set up a rock band, lived in Baghdad during the Iraq War and nearly died in a helicopter crash.
Apart from that, he was one of the first developers of the technology that would become Google Maps, and has been credited with coining the phrase "cloud computing". Coder O'Sullivan helped set up mapping software company MapInfo and floated it in 1994.
His shares were worth $17m before he cashed out to fund start-ups and other early-stage investments. These included punts on Apple, Netflix and video game company Harmonix.
The former Dragon's Den star has estimated that his Apple shares would be worth close to $500m - if he'd held on to them… but he did make a 30-fold return on his stake in Netflix.
The Cork-based investor now runs his SOS Ventures, which has made good money from exits including Storyful, Collaborate.com, Mapflow and Global Protein Solutions.