Mobile payment systems like Isis promise a world where paying for something is as easy as waving your cellphone over a store terminal. But what if all you had to do was nod?

That's the promise of Eaze, a Google Glass app launching in beta on Friday that lets Glass users hook up a virtual Bitcoin wallet to make payments. You first activate Eaze with a voice command, TechCrunch reported; then, use Glass' camera to scan a QR code that the store will provide. A double nod completes the transaction.

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It's all very clever and convenient, although Eaze obviously requires that the store accept Bitcoin. If it does, the clerk will be able to generate the code and present it to the Glass wearer on a tablet or other display. The retailer doesn't need to support Eaze specifically; the QR codes are the same as any other Bitcoin transaction. The company breaks down the process in a video:

The app just provides the means to make the transaction with Glass; it's not a virtual wallet itself. A user will need to link the app with an existing wallet, and it supports Coinbase and Blockchain to begin. The company says it has plans to add support to regular currencies like dollars and euros as well as link the app with PayPal, although those upgrades won't come until summer at the earliest.

Eaze obviously makes payment incredibly convenient. It also makes Glass a more tempting target for thieves. Glass already has a screen lock, but Eaze says a future update to the app will add the ability to set a spending limit that can't be changed without a PIN.

Although Google Glass is Eaze's first home for its payment technology, the company has plans to port the app to other wearables, including smartwatches, bracelets and even rings. Eaze says the cost of the service is free — "for now."

Eaze isn't the first payment app for Glass. Pay With Wallaby, from developer Wallaby Financial, also lets Glass users hook up a virtual wallet to the device and pay via QR code. Another app, GlassPay, is in development, and Google itself reportedly will soon introduce Google Wallet to Glass.