Can it be done in secular life? I assume you mean something like "can people do Tummo in the morning, during their morning session, and then go to the office to do their job, etc.??"
Well....yes, it can....but successfully? Not likely.
Seriously, though.....Tummo is a retreat practice. Actually, there are different "tummo practices" though they're all based on similar foundations and techniques. There's a reason why it's normally taught in retreat...first, one needs the preliminaries to lay the groundwork--this includes deity yoga as well as ngondro, etc. Tummo is profound practice, and it requires a certain "outlook" that would be hard to attain and/or maintain with the distractions of daily life.
But I think that once someone has actually "actualized" tummo--practiced it to the point that one has experienced it, let's say--it may be possible to carry through in what you call "secular" life, which I take to mean "outside of a strict retreat."