do demos utilize the engine of et, and therefore utilize opengl? if so, you might rather forget about that project - or else write some convenient wrapper (maybe best two-layered.. principal architecture and language-derived library for basic io with et), after you found a way of playing them without having to install et on each supported phone. just in case you want to play the demo files themselves and those do make use of the engine.
you may want to write an on-the-fly rendering-service as web-based service, which then provides videos, like youtube does it (or uses youtube for storage, if possible). this way you can supply demos as is and still allow ppl to watch rendered scenes via phone. and it's way easier, though not more than an idea - there would be some overhead for creating process / administration level functions, supplying a decent link to the file and so on..