Ektar 100 in 110 (pocket camera)?

Why not?

"World's finest grain" as they state on the box should fit well to the small negative size...

I see no reason this shouldn't work in any 16mm camera that doesn't depend on cine perfs. For 110, you'd need to reload a cartridge and use it in a camera that works without the single perf per frame of the original film; it would surely be easier to use this film (slit from 35mm or 120) in a Minolta 16 MGs or QT, or in a Kiev 30 or 303 (same frame size as 110, but work normally with unperfed film).

Ektachrome 100 & Vision3 50 et al stocks are available in 16mm single-perf. Both are probably finer grained than Ektar 100.