At the moment this App support only user apps, perhaps this will be extended for System Apps.
Tags: share, apk, aplication, program, bluetooth, nfc, sharing, app info, apk info, launch app,
Tags: nfc share apk, share apk with nfc, share my apps, my app share, nfc apk share, nfc file share apk, share my application, nfc quick actions apk.
Supporting Only user Apps, perhaps the System Apps will be supported soon.
Sharing the APK with Gmail its "buggy" seems Gmails change the way to attach a file. so you can "see" the APK but you cant send, you can use k9 mail or other client and will work.