Is it possible to integrate CiviCRM with a hosted VOIP solution?
There isn't a single unified VOIP interface, so each interface with civi would have to be custom.

I've seen two interfaces with an Asterisk based VOIP:
- fetch the name of the caller (based on the number) to display it on the phone when ringing
- add click to call on various screen (at least the contact details)
- log a call

For the last one, I don't think it has never been very useful, because most of the callers don't seem to think most of the calls are important enough

Neither of these were hard to develop, but as said, it's probably quite specific to what is your VOIP solution.