Hi Gary,
Note: I'm one of the developers/maintainers for it.
The plugin should work on 2.7, and has been tested a bit there to verify as such. What currently does not work there is the login indicator (as it relies on the legacy log table).
I've not tested it against Moodle 2.8 yet, I'd expect it would still work on 2.8 much the same as it does in 2.7 (again, with the login indicator not yet working).
Updating the login indicator to work on M2.7+ is on my TODO list. Unfortunately I don't really have a timeline for you for when that will happen just yet.
As with any plugin, I'd recommend testing it on a test instance of moodle first to make sure it works nicely on your specific version (and with any customizations you have).