Can Bangle.js 2 app disconnect from phone and later reconnect?

I know that Bangle.js 2 only supports one Bluetooth connection at a time, but is it possible to make an app that does the following:

(Bangle.js 2 is connected to Android phone and Gadgetbridge on that phone)

• app disconnects Bangle.js 2 from phone
  
• app connects Bangle.js 2 to some other device
  
• app disconnects Bangle.js 2 from that other device
  
• app reconnects Bangle.js 2 back to the phone
  
  

(Bangle.js 2 is again connected to phone and communication with Gadgetbridge continues normally)

It is the other way. Phone connects to Bangle. And you can have another connection from bangle to some other device. The limit is one connection in and one out.
Maybe my answer to you here was confusing? Bangle is not the active side that starts the connection when gadgetbridge or webide or bangleapps site connects to it.
So you can have another connection out while phone is connected.

Well except the iOS case, there it is slightly more complicated with notifications but I think even there you can have one connection out while iPhone is connected.

Also your 4th point "app reconnects Bangle.js 2 back to the phone" is hard to do because the connection is done in reverse. However maybe if watch notices the phone disconnected it could start some connection the other way to ping the phone to reconnect. But gadgetbridge would need to provide service for accepting that.

As @fanoush says you can't make a device connect...

However you could potentially use NRF.disconnect() to force a disconnect and then NRF.setMACAddress to change your Bangle's MAC address.

Then, as long as both of those devices auto-connected as soon as they saw 'their' Bangle's MAC address you could do what you want.

Can the iPhone use its clock to regulate Bangle.js 2's time? By sending the time at certain (infrequent) intervals?

If there were an app on the iPhone, yes. I'm not sure if the iPhone itself has a time service though.

I'm not sure if the iPhone itself has a time service though.

It does according to documentation https://developer.apple.com/forums/thread/5279

Pairing or otherwise connecting Bangle.js 2 to an iOS phone through Bluetooth seems a challenge. Apple says contact your device manufacturer to see if it supports iOS.

(Bringing in GPS time may still be the way, but I can't get it to work on Bangle.js 2 the way it seems to have worked on Bangle.js 1.)

Pairing or otherwise connecting Bangle.js 2 to an iOS phone through Bluetooth seems a challenge.

Did you install the iOS app on the Bangle first? Seems to work great for me

[Post reposted in the smartphone thread:
Is it possible to sync Bangle.js 2 time to smartphone time?

AFAIK, that question has not been answered, not for iPhones, at least.]