NEW DELHI—Early last year, product planners at India’s best-selling phone maker decided consumers wanted a handset that could be operated in many of the country’s 20-plus official languages.

Four months later, Micromax Informatics Ltd. unveiled the $110 Unite, which let users label their apps, type, send messages and interact on social media in 21 different scripts—from Marathi and Gujarati to Tamil—rather than just English and Hindi, as is common for Indian phones.

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