The Echo Input sold in the Amazon Prime sale in July 2019 for just £14.99 but does not come with a speaker and you must connect your own. Anything basic will do or you can link it to something more powerful.
Audio is sent, via a 3.5mm plug, to any device like the Sonoro DAB pictured below.
If you already use a speaker, or other device like a TV soundbar, it can be easily shared with an Echo Input using a "Y" cable splitter that can be purchased for a couple of pounds.
Just search eBay for a "3.5mm Audio Splitter Stereo Cable 1 Male to 2 Female Jack Headphone Headset"
The Echo family requires the "Alexa" wake word followed by your command which it will then execute.
This is Amazons' equivalent to using Google's "O.K. Google" trigger phrase that activates the Google Assistant used in the Nest Home Speaker product line.
Control your Echo with voice commands or use the Amazon Alexa App.
If you already have an Amazon Account you can click here to view your Amazon Apps.
If you are interested in Amazon Fire devices, that also feature Alexa, then click here for examples.