No question I loved my 2014/2017 B250e but alas the lease ended and I returned them which in hindsight was a mistake. I timed it badly as I thought the EQC was going to be sold in the US. So I leased an ICE MB but am prepared to turn it in for a EQB in 2022/2023.
To your questions, yes the primary use for the apps was to see the state of charge remotely. I am not aware of any apps or devices that anyone has perfected to monitor the B250e remotely. If I still had my B250e today, I would first just calculate when my car would fully charge which is pretty easy. What you can't tell is if someone unplugged you. I don't believe that any software upgrades are coming.
This may sound stupid but here is a workaround (cheap or expensive). There are battery powered wireless cameras that go for under $50 but it needs a wifi signal to control it from your smartphone. Then you can monitor the ClipperCreek lights (I am not that familiar with those chargers) to see if it is still charging or monitor the panel on a ChargePoint kiosk. So if the CC charger is at work and there is wifi, voila. If in a public setting, you would need an active mobile wifi hotspot device for the camera to connect to. Not worth the extra expense but okay if you want to check on your car from time to time.
Personally, I got used to not knowing and did experience a couple of times when the charger was bad and came back to the same charge level as when I left it there.