Came over to see if you had heard...
Nice bit of info here at the wellspring:

www.pbs.org/wgbh/masterpiece/contemporary/host.html.

I think he has a strong teaching mission in his psyche. Having brought a whole new audience to Shakespeare, he now is hoping to have the same effect for PBS.

He seemed very at home in that Red Nose sketch with Catherine Tate where he played an English teacher, didn't he? :)

This is a very low level commitment, and therefore there might not be much thought behind it. He may be appearing in some of the dramas shown (Recovery, Learners come to mind), and he was asked to do it, and he said yes. A day's work, won't take more than that.

He probably taped all the introductions in one sitting. Probably never even left the UK. So this was at most a couple days work in exchange for an easy paycheque and some minor exposure in a new market.

Maybe he has got the hosting bug, after the comic relief presenting?...Whatever the reason, he isn't one to shy away from most things....I mean despite his fame to claim with DW, you will still find him doing the odd bodd advert...and as others have said, it probably won't take much of his time recording a few introductions....
best of luck to DT no matter what he does...

He's already appeared on Masterpiece Theatre (before the big "Masterpiece..." rebranding) in Casanova.

So now we've had Gillian Anderson (Classic) and Alan Cumming (Mystery!) and now Tennant (Contemporary). In a way, perhaps, Rebecca Eaton (Masterpiece producer) is trying to lure in the geek audience...

OK, I had a response in my head, and then Ryan H. beat me to it. So: what he said. And a tip of the hat to Ryan H.

I'm with Ryan and Mimi. This seems like the various voiceovers he's done - the documentary about doctors on Everest, Swarm, etc.

He seems to plan his major moves pretty carefully (ie DW, Shakespeare, etc) but then fits in whatever small jobs appeal to him on the side, when mere mortals would be relaxing!

I am in agreement with the other posters here. DT seems to never sleep, what with DW; voiceovers; narration; audiobooks (am listening to his Quite Ugly One Morning at the moment, and loving it!); publicity; etc. this guy doesn't know the meaning of rest.

Easy job, exposure, and following in the footsteps of fellow Scot - Alan Cummings.

It's a start at getting more widely known in the US. Julie Gardner and Jane Tranter are already in LA and RTD has recently been spotted queueing for a work visa at the US Embassy. I wouldn't be surprised to see DT doing something more substantive there, although I can't see a long running series on the cards. A movie role perhaps?

DT strikes me as being very savvy about his career. I found an old interview where he listed the roles he would like to play in future and a number of those have already been ticked off.

DT has always done lots of varied projects, even with the overwhelming workload of Doctor Who. He fitted in a cameo for the film "1939" between Hamlet finishing its run in Stratford and transferring to London. He's done several narrations for documentaries shown recently, plus one for an astronomy exhibition, hosted and guested on radio shows, and isn't too proud to do voiceovers for Tesco supermarket ads!! This new gig looks just his thing!

It doesn't surprise me, honestly. I've found that good character actors are often the hosts for Masterpiece Theatre. It's a great way to introduce them to the audience here in the States. Gillian Anderson was well-known here due to the X-Files, of course. I hope it's a good intro to get Tennant known over here, too.

This is a smart, professional move. The point of joining PBS as a host is not simply to get easy money. The hosts of these series get invited to all the right parties and meet all the right people - the monied elite who fund the network (which is made possible solely by donations), support the arts, and invest in Broadway shows or Hollywood films. Producers and directors like Steven Spielberg, Ron Howard, George Clooney, Tom Hanks, Clint Eastwood, et al, not only watch PBS programming, but are important contributors, who also attend screenings to which David will be invited. Being a mere performer in a drama on the network does not give him access to these people. Being a presenter does.

It also gives him prestige. Much more than he would attain if he started his career in the US by doing anything other than Hamlet on Broadway. Who knows? Maybe that's next! In my opinion, "David Tennant, award-winning dramatic actor of stage and screen" is a better career move than "David Tennant, Hollywood heartthrob".

DT seems to be a workaholic (plus he doesn't limit himself to just television work but does the audiobooks, radio, plays, etc.) and I doubt this will take much of his time anyway to film so he can continue with his post-DW work. I'll happily watch the intros that he does for the show (more likely than not, I would have already purchased the show in R2 format already so wouldn't necessary watch the edited version of the show).

Gee above mentioned David narrating documentaries. He has done a recent one that is on Youtube, if you can't get it in other ways. It is about Monty Python and the town of Aberystwyth in Wales, where the film was banned for 30 years until and actress in the movie became mayor. It was written and directed by James Strong who directed some episodes of DW.

David just adds so much to these types of shows with his narration.

As a Doctor Who fan... David Tennant rocks. As a David Tennant fan... I'll watch any role he takes on. Scottland to England to America, Broadway to Hollywood, Hearthrob or character role David is enlightening, energetic, and enthralling! Whatever he takes on I'm sure it will be a smashing hit.Good luck and God bless you David.