When I read Rainbow Six, I remember wondering if he wrote parts of it to be more applicable in the video game, a la Splinter Cell. The heartbeat monitor, the map types (jungle, city, amusement park)... it seemed like nice fit.
Weren't they made at the same time, in fact? Edit: Mind you, I only know this because I looked it up after having that exact thought reading the book :)
Yeah, according to this wiki citation[0], the tie-ins were a bit ad-hoc but the game plot was actually finalized before the book was done, which accounts for the discrepancies. So there's no real way of knowing what started out as a game mechanic.
Worked out better than Splinter Cell, anyway-- I don't think I got through more than a page of the novelization. (Which wasn't written by Clancy, FWIW.)
I remember having the same thought with that book. Elements of the book seemed to be there for the benefit of spin-off video games, much like you'll sometimes find a character in a movie probably exists for merchandizing.
Maybe I gave him too little credit in this case. Either he was familiar with prototype tech that we aren't aware of yet, or he was actually a decent near-future sci-fi writer.
They were still a good read though.