[Symbiote]

In Scandinavia, usually just by showing the "payment sent" screen to the merchant. The merchant can check their own device for the notification if they want confirmation.

The annoying background video shows it: http://mobilepay.dk/da-dk/Pages/mobilepay.aspx

[raverbashing]

Seems a bit slower than NFC, but I haven't seen it in action

(and the payment sent screen can be spoofed)

For tips it seems fine

[jeekl]

For most situations, spoofing a sent-screen that usually displays the vendor or persons name, is not too easy to do in the heat of the moment, without preparation, so it's not really been a problem yet.