I was doing some shots with my Olympus E-PL1 Micro Four Thirds camera for another thread, and noticed it has three different spot metering modes: normal, hi and low. They are poorly documented, so I tried them out.
The hi mode is essentially an expose-to-the-right mode! When you're in that mode and point at the brightest spot in the scene, the camera will expose that spot for higlights, instead of middle grey. I did numerous test shots around my apartment, and almost all were very nicely ETTRd with no channel blowing out. Histograms verified in Lightroom. There were two or three which had blown highlights and one which was underexposed, but I suspect this has something to do with the limited accuracy of a 2% spot meter.
It's not fully automatic, of course. You have to determine which is the brightest spot in the scene and ETTR that. Everything brighter will be blown out. Technically I can see a fully automatic ETTR mode to be possible, but desirability is another matter. How to deal with specular highlights and how much image area is allowed to blow out should be left to the operator - those who care about ETTR are probably proficient enough to make that call themselves.
It is unclear how the camera determines the exposure in this mode. As it's doing it on the fly and you can see the results live on the screen, it must be using RAW data instead of in-camera JPEG - whether it uses all three color channels is another matter. In any case, it's a very exciting feature, something which many, including me, have been asking for on digital cameras. I'll do some further tests on its utility and reliability in real-life shooting outside this weekend.
There is also low mode which exposes the spot for shadows, utility of which I have not yet fully figured out. I guess you could drown out anything darker than the spot you're measuring with it, which could be useful for those who don't post-process their photos.
Attached demonstration with three frames, red spots mark where I put the highlight spot.