Google Tag Manager Site-Wide Message

I would like to be able to publish urgent/site wide type messages. The type of message that is then seen on every page / hub of the site e.g. “We are still in Beta with the site please click here to provide feedback”.

Is there an approach that supports this within Bloomreach or would I be better to look at using Google tag manager to inject some code or a template that allows us to get a message out across an entire sites content.