It's more the other way round: The editor Lyx uses LaTeX and maemotex is a slimed-down version of latex for maemo. There is no native Lyx for maemo (and I doubt there will ever be) and no other editor can use Lyx files (you can always export Lyx->LaTeX, but I guess that's not what you want.

But you can use Easy Debian and install Lyx there. It won't be optimized for the small screen and compiling might take some time but I guess it should be pretty usable. Easy Debian is in extras now and to install Lyx just use from the easy debian command line.