This has been answered before here: how do I open iphone apps via phonegap
"The only way that one app, PhoneGap-based or otherwise, can cause
another app to launch is to open an URL "
Opening Contacts:
You would need a "URL scheme" such as the one defined here:
// In config.xml
<gap:url-scheme>
<scheme>app1scheme</scheme>
</gap:url-scheme>
Then from your other app you'll just have a link to app1scheme://, eg simply
<a href="app1scheme://">Start App1</a>
Contacts Database:
If you have not already, you can access the "Contacts database" using PhoneGap:
iOS (in the named application directory's config.xml)
<feature name="Contacts">
<param name="ios-package" value="CDVContacts" />
</feature>
Source: http://docs.phonegap.com/en/edge/cordova_contacts_contacts.md.html#Contacts
Another Example, without PhoneGap(accessing the Calender):
<a href="calendar://">Click me!</a>
Now go to your iOS app's info.plist file. In that add the following tags:
<key>CFBundleURLTypes</key>
<array>
<dict>
<key>CFBundleURLName</key>
<string>com.companyname.appname</string>
<key>CFBundleURLSchemes</key>
<array>
<string>calendar</string>
</array>
</dict>
</array>
Save the plist file and exit it. After this when you open the web page in Safari browser of your iOS device and click on the link, your iOS app will invoke. I hope it helps!
Source: https://stackoverflow.com/a/7658785/950427