Looks like it has now been announced for general use so there is a proper thread on it over at myenergi now.
I'll continue to set charges via the app until I see several others confirming that this works reliably. Will be very useful when it does but at the moment I go with whatever Octopus Watch recommends for whichever charge period I choose (additional savings using the Zappi Agile feature will be a few pence on most occasions anyway).
There’s no harm setting a price threshold/specific kW top up figure on the myenergi account and then checking the app shortly after Agile prices are released to see if the timers have been pushed through successfully. I’ve been using for about 6 weeks now and had 3 failures- two of which were linked to security change on the servers and they locked themselves out. So it hasn’t been a real issue, but there are still one or two bugs in unique situations.
Thanks @CMc1 - that's encouraging but I'll still wait until people confirm that every charge has worked. With another lockdown the car won't be used much so I'll just keep an eye on daily Octopus Watch recommendations for occasional top ups when needed. So far I've managed with 'manual' timed charges at ~5p average... often well below.