In a nutshell, what you have is a wireless dongle and a plastic casing containing a speaker and a mic. £40 worth of plastic. Total waste of money. Sound quality ...questionable, muffled at best. Look like an LCD in the picture? WRONG! its an LED flashing the word SITECOM, no LCD display, serves no purpose whatsoever. Again, useless.
Works with all VoiP apps? Hmmm...let me see, so does every PC phone that has a mic and a speaker. What you wont see on any description is that the driver software program is bespoke to Skype. This means that the buttons on the phone can only be used with the Skype software, no other VoiP application can use the buttons as the driver software is customised to use Skype. Again, misleading.
If it ever comes down to £20, then still avoid it. I bought one and now I'm stuck with it. I'll use it until I see something better, which shouldnt take that long then this piece of useless overpriced equipment is going where it belongs. In the bin. Enough said.