MyActivity.java

    public boolean hasOficialPackage() {
        Intent intent = new Intent("...");
        PackageManager pm = getPackageManager();

        // Queries for Packages that can handle a given Intent
        List<ResolveInfo> resolvedActivityList = pm.queryIntentActivities(intent, 0);
        for (ResolveInfo ri: resolvedActivityList) {
            // Is this the package we'e looking for?
            if (ri.activityInfo.packageName.equals("my.package.name")) {
                try {
                    // This is the package we want. Retrieve signatures!
                    PackageInfo pi = pm.getPackageInfo(ri.activityInfo.packageName, PackageManager.GET_SIGNATURES);
                    for (Signature signature : pi.signatures) {
                        
                        // Should validate the signature correctly. Using this for the sake of brevity.
                        if (signature.toString().equals("expected_sig")) {
                            return true;
                        }
                    }
                } catch (PackageManager.NameNotFoundException ex) {
                    // Shouldn't happen, as we've just retrieved the name from PackageManager.
                    // Log the error, and continue looking.
                    Log.d("MyActivity", "Package " + ri.activityInfo.packageName + "not found");
                }
            }
        }
        return false;
    }