Google’s Chromecast series of streaming devices has had a few iterations in its decade-plus on the market. When it launched in 2013, the product category of low-priced streaming sticks/boxes/dongles didn’t exist, and Google basically created it with their $34.99 MSRP product. In that first iteration, Chromecast had no remote control or user interface, instead entirely being a receiver for content queued up using each streaming service’s mobile app or website as the remote. The second generation improved performance while changing the form factor, and the third generation made them full-fledged Google TV devices, complete with remote, where casting is a feature, not the whole product.
The second generation, though, also included the launch of a second product, one that was killed off before the third generation’s debut. That would be Chromecast Audio, which was priced identically to the main HDMI model but instead featured an audio-only output via a dual-function 3.5mm jack that served both analog (over traditional AUX cables) and digital (via Mini TOSLINK) audio. Though owners of soundbars or AV receivers might already be able to use the traditional Chromecast via HDMI, the Chromecast Audio opened the ecosystem up to Bluetooth speakers, shelf/mini systems, integrated amps, and other audio hardware that could accept AUX or TOSLINK input. For example, you could use it to wirelessly send music to a Bluetooth speaker without having to route call audio to it.
Unfortunately, Google killed Chromecast Audio in January 2019 without explanation. Presumably, its niche wasn’t big enough to justify continued manufacturing.