Bill Parcells - Wikipedia says Parcells did media in his years between NYG and NEP, and again between NYJ and DAL, and again between DAL and MIA. I personally didn't find him to be too entertaining, but in any case he was a big name and the media was very willing to hire him. The article says he was offered the Monday Night Football gig which is a very high prestige gig IMHO, but he refused it.
I also think that in years gone by a media gig was less prestigious than a head coach or GM gig, but these days media is king and no one looks down at Gruden et al for cashing in. Personally I think it is getting a bit tiring to see all the Gruden speculation every season or two. He's making the big bucks and holding down a prestigious job, and I can't see why he'd want to do what his brother does for a living when he can just do the MNF gig.