Thanks for your detailed comment! Let me address a few of the points.
To your Slack suggestion: there are many learnings from psychology and team work that make stickies on a wall a much better choice than any digital tool — too many to list here. For experienced agile teams (i.e. teams who have been working together for a few months and also have been practicing agile for years), the Slack solution can actually work (I work this way with two teams) — though it requires more effort on part of the team than standing in front of a wall. Experienced teams know the drawbacks of digital tools and distributed teams and so they will put extra effort into compensating this — I wouldn’t recommend the Slack solution for inexperienced teams though.
As to how you actually know, whether someone calling themselves “agile coach” can actually improve performance? Well, that’s the tricky part and I don’t have a definite answer. The bad thing of something good like Scrum becoming mainstream is, that a lot of people smell money and are not interested in improving teams. I would say, the chance to get a bad coach in todays market is > 50% — sadly. How to find the good ones? I would prefer people WITHOUT a certificate! Because someone who does Scrum and has no certificate is likely in it for the real benefits of Scrum instead of just the money. This doesn’t mean that coaches with certificates are necessarily bad, but I personally see a higher chance of picking people who can actually help, if I pick from the bunch of those WITHOUT certificates.
To find a good agile coach, also look at their track record: have they turned around teams or companies in the past? Have they worked in an agile manner as part of Scrum teams (i.e. as a developer)? This might indicate a coach who can actually improve things for you.
And to address your “top management driven” concern: Scrum and agile has historically been a grass roots movement by development teams, who wanted to work better — management had been rejecting this agile idea for more than a decade! Just recently it became obvious that Scrum and agile are so superior to most traditional ways of working, that management had to jump the train. And now some managements actually try to push agile into the organization without any understanding of what agile is — that is sad and leads to some of the bad rep agile gets recently.
Scrum was actually driven by developers, who wanted to control those pesky business people — not the other way round! Because business usually told the teams what to do, how to do it and how much time it should take — which is insane! Scrum gives the team a mechanism to say: look, we know HOW to do this (we studied it and have years of experience!) and we know how long it will take — so just tell us WHAT to do and leave us alone. Much more freedom for the developers. This now forces business to get structured in what they pass to the teams! Before Scrum, management was often just winging it, pushing work to the team randomly and then screaming at them, if the results were bad. Scrum forces management to finally organize and do their freaking work!
So Scrum is definitely not a way for management to control pesky techies — it’s more a way for the developers doing the actual work to control management, so that they do their homework :).