There is no widely known or established app called "Equinox" specifically for Android. It[SQ]s possible :

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The name is slightly different:

There might be a similar-sounding app. Could you be thinking of a different name? A small spelling variation could make a big difference in search results.
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It[SQ]s a very niche app:

The app might be extremely specialized, with a small user base, or only available in certain regions.
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It[SQ]s a new or unreleased app:

The app could be very recently released or still under development.
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It[SQ]s a private or internal app:

The app might be for internal use within a company or organization and not publicly available on the Google Play Store.

To help me find what you[SQ]re looking for, please provide more details:

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What does the app do?

(e.g., fitness tracking, calendar, game, etc.)
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Any other keywords you remember about the app?

(e.g., its icon, colors, a specific feature)
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Where did you hear about this app?

(e.g., a friend, an advertisement, a website)

With more information, I can help you find the Android app you[SQ]re looking for or determine if it exists.