The accessory joins the night light and motion sensor accessories that already exist for the Flex, but you can only plug in one at a time, which is a shame.

The smart clock is the same price as the other attachments at £15 / $15, which some feel is a bit pricey given the Flex only costs £25 itself. But it's an inexpensive way to bring the Alexa assistant to any plug socket on the cheap.

Just note that Amazon also sells a version of the Echo Dot with a built-in clock. 

You can buy the Smart Clock for Echo Flex now for $15 in the US and for £15 from Amazon in the UK.