start Implicit intent and allow them to download if that external activity is not available.
Intent intent =new Intent(Intent.ACTION_DIAL, Uri.parse(“tel:555-2368”)); // Check if an Activity exists to perform this action. PackageManager pm = getPackageManager(); ComponentName cn = intent.resolveActivity(pm); if (cn == null) { // If there is no Activity available to perform the action // Check to see if the Google Play Store is available. Uri marketUri = Uri.parse(“market://search?q=pname:com.myapp.packagename”); Intent marketIntent = new Intent(Intent.ACTION_VIEW).setData(marketUri); // If the Google Play Store is available, use it to download an application // capable of performing the required action. Otherwise, log an // error. if (marketIntent.resolveActivity...