SAN FRANCISCO  Kara Lynn has amyotrophic lateral sclerosis, or A.L.S., which has attacked the muscles around her mouth and throat, removing her ability to speak. A couple of years ago, she spent more than $8,000 to buy a computer, approved by Medicare, that turns typed words into speech that her family, friends and doctors can hear.

Under government insurance requirements, the maker of the PC, which ran ordinary Microsoft Windows software, had to block any nonspeech functions, like sending e-mail or browsing the Web.

Dismayed by the PC’s limitations and clunky design, Ms. Lynn turned to a $300 iPhone 3G from Apple running $150 text-to-speech software. Ms. Lynn, who is 48 and lives in Poughkeepsie, N.Y., said it worked better and let her “wear her voice” around her neck while snuggling with her 5-year-old son, Aiden, who has Down syndrome.

Medicare and private health insurers decline to cover cheap devices like iPhones and netbook PCs that can help the speech-impaired, despite their usefulness and lower cost.