You can input the name or id of the echo using any msg property you wish. In this example I have use msg.payload
e.g.
[{"id":"d4e55e1616b67743","type":"inject","z":"b9860b4b9de8c8da","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"G056756df430C6","payloadType":"str","x":160,"y":3060,"wires":[["7e86a25a34159dd7"]]},{"id":"d0bf7757ada5ae32","type":"inject","z":"b9860b4b9de8c8da","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"Lounge","payloadType":"str","x":150,"y":3020,"wires":[["7e86a25a34159dd7"]]},{"id":"7e86a25a34159dd7","type":"alexa-remote-echo","z":"b9860b4b9de8c8da","name":"","account":"c8738129.d902c","config":{"option":"get","value":{"what":"bluetooth","device":{"type":"msg","value":"payload"}}},"x":390,"y":3020,"wires":[["ed8a158fd90c551c"]]},{"id":"ed8a158fd90c551c","type":"debug","z":"b9860b4b9de8c8da","name":"debug 324","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","statusVal":"","statusType":"auto","x":490,"y":3100,"wires":[]},{"id":"c8738129.d902c","type":"alexa-remote-account","name":"alexa remote 2","authMethod":"proxy","proxyOwnIp":"localhost","proxyPort":"3456","cookieFile":"","refreshInterval":"14","alexaServiceHost":"layla.amazon.co.uk","amazonPage":"amazon.co.uk","acceptLanguage":"en-GB","onKeywordInLanguage":"","userAgent":"","useWsMqtt":"on","autoInit":"off"}]