By Simple Multimedia Cell Phone , do you mean Feature phone ?
Quoting from ET, Feature phones are all set to continue dominating the market with a more than 50 per cent share as they remain the preference of people in small towns and rural areas who have little need for or money to buy smartphones.
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There is more info online to suggest there is a feature phone market in emerging markets throughout the world.
Your best bet is to tie up with existing feature phone manufacturers like a Micromax , Lava, Samsung as an OEM on the mobile accessories side.
All the best.