I have a Homebridge setup using the Tonesto bridge. Works fine, and puts the devices into a client's IPad. They don't have a HomePod or a Apple TV. (Call this Bridge "A"). I use this because it also adds the feed from a few Ring Cameras.
The client wants to access (just the Hubitat devices), as well, on her IPhone. However, when I put the HomeKit app on her IPhone, and try and use the previously mentioned bridge, it gives me an error message to the effect that the accessory (Bridge A), is already is somebody's home.
Can I use the built in Hubitat to HomeKit bridge, and get another accessory number and use it on the client's IPhone?
Yes, you can use both at the same time on the same hub (or same Home, but only one at a time with how Apple's "pairing" works, which I think is your existing problem).
So, this is an Apple question.
In other words, can I use one accessory bridge on an IPad, and a different accessory bridge on an IPhone (that are on the same wifi network)?
Pretty sure Apple Home will show the same thing on all mobile devices. Unless you create multiple homes perhaps, with one bridge added to home x and the other bridge added to home y.
Then you could pull up home x on iPad, and home y on iPhone while using each device.
But in general your home can’t have only devices a, b and c (from bridge x) show up on your iPad, with only devices d, e and f (from bridge y) showing up on your phone.
The error is normal you can only pair a bridge to one "Home".
If they had both the iPad and iPhone on the same apple ID then the devices would show on both. Or they could also just share the home from the iPad to the iPhone account.
As stated, you can also use a different bridge (the system integration) to share devices to a separate "Home" in Apple HK.