You need a Tradfri gateway to use the shortcut key, and connected devices (such as smart lights or speakers) need the IKEA Home app for iOS or Android. According to the instruction manual published in the FCC list, the device should last for two years before the battery needs to be replaced.
Teknikveckan suggests adding different icons to the button to indicate which scene controls them. The photo in the FCC file shows the device with a bed and a moon on the front. Unfortunately, the leak did not indicate when IKEA could release the device or how much it would cost. However, as The Verge points out, it will probably cost less than other smart home hubs.