Devices running Android Lollipop or newer have this feature built-in, but a lot of pre-Lollipop devices do not.
That's why I have reverse engineered this app.
NOTE: this is still a work in progress, so please send me an e-mail if you run in to any problems.
For now you will need a third-party app (or an Android Lollipop device) to prepare an NFC tag.
Please help me with the translation of Wi-Fi tag: