Palm Treo/Pre and BlackBerry users! And probably Clicks users too. It's not a matter of "Does Russian language use the Latin script?" (it doesn't), but rather "What is the least annoying method to input Cyrillic on a BB-style keyboard, which doesn't have enough buttons for the йцукен layout?". Phonetic layouts such as яверты or яшерты were very popular for such devices back in the day.

I’m considering the linked-above device to replace my mom’s Q10 later this year, so this is a specifically helpful answer for me — thanks!