If you’re interested in diving deeper into Professor Fritz’s research on developer flow states, check out his list of publications.
Flow states can be affected by things as simple as the right lighting, so Logitech created keyboards that automatically adjust their keyboard backlighting.
Lights can be used to indicate your interruptibility.; Prof. Fritz did some research on FlowLight, which indicates your willingness to be interrupted with a simple red light/green light protocol. These days, you can use your Slack status to the same effect.
If you’re looking for apps to improve your daily flow, Cassidy recommends Centered.