You can’t do it easily since other apps may (and most likely) offer another API that is different than youtube.
For example:
youtube search API:
https://www.youtube.com/results?search_query=facebook
facebook search API:
http://www.facebook.com/search/web/direct_search.php?q=%gmail
gmail search API:
Gmail: http://mail.google.com/mail/?search=query&view=tl&start=0&init=1&fs=1&q=%youtube
You see there is a different pattern. Thus, you need to implement it manually, 1 by 1, and according to the search API offered by every single app.
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solved search in another application