Level RF- now Soylent (disclaimer:involved as ex-founder)
ViaCycle -same YC class as LevelRF/Soylent
Paul Stamatiou is a prolific entrepreneur/YC alum.
InstantCab is a YC company started by Tech alums.
--------additional------ Chris Quintero -ME 2011, went on to help start http://bolt.io
Bractlet is a GT alum company that is now in the surge accelerator program in Houston.
CallRail and Design-A-mosaic are both founded by GT alum Kevin Mann.
Robotic dragonflies came out of a kickstarter project.
Titintech came out of GT as well from a Mechanical engineer.(disclaimer:involved in Rice BPC)
One of the first VSats was launched by GT alums- Steve Chaddick who later went on to start Ciena, a massive telecommunications company.
There seems to be a set of people who 'have to be entrepreneurs' and there's a set that 'want to be.' IMHO, The set of people that 'have to be' can be pushed anywhere and don't have as big a concern about coworking spaces,environment, meetups, hackathons etc..
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I myself failed 2 physical product ventures(thermoelectric at JumpStartFoundry and LevelRF at YC) while at GT and also worked for 2 at the ATDC that were both venture backed and had physical technologies.
------------------------------ Interesting post in any case.