The app, which allows users to generate their own wallpaper adapted from the film's original poster design, has had over 50,000 hits in ten days.
Fans of the movie are able to customise desktops, mobile displays, profile pictures, Facebook cover images and Twitter backgrounds through the app.
Khan is also promoting the action film through a series of announcements at railway stations around India.
He has recorded 15-second sound clips that are being played at 125 stations across the country.
"It was such a pleasant surprise to hear Salman Khan at the railway platform instead of the regular announcers one fine morning while rushing to work," said passenger Bhavna Seghal.
The Yash Raj project is currently the second highest-grossing Hindi film after Aamir Khan's 3 Idiots.
Watch the trailer for Ek Tha Tiger below: