What replaces this bit of HAL?

[Tom Horsley]

I keep reading that HAL is going away to be replaced by
a scattering of separate bits, but I can't figure out
what is supposed to replace HAL to achieve the equivalent
in a program I'm working on:

This program recognizes PTP capable cameras that are plugged
and unplugged from time to time. I get DBUS system messages
(containing the HAL udi string) on the plug/unplug event,
and I can lookup things like the USB bus and device numbers
which are needed by libgphoto2 by calling HAL functions to
query properties.

So if HAL is going away, what the heck is the official
recommended way to achieve these same results without HAL?