WallIT,
I must agree with dwayneg on this one as it is very difficult to get some devices working the way everyone "thinks" it should work on a system that has not been vetted by Mitel. The last SIP device that I did was a wireless conference phone (SIP) and it took forever to get it to work and after that there were still unforeseen issues that took awhile to get fixed with the manufacturers tech support that the customer had to pay for. The worst problem I had was that the phone would reset during a conference call at about the 10 minute mark and it was how it was trying to update with the Mitel system during a conference call that caused the problem.
The other issue you are probably not thinking about is when you use a device that is SIP based, since Mitel doesn't have an IP based wireless conference phone solution, is that you are stuck with the devices SIP capabilities which do impose limits. Case in point the SIP Conference phone I mentioned above only allows a 3-party conference from the phone so if you want to get a larger conference call started you would have to do it from a standard Mitel 5000 phone or use the Meet-me Conferencing feature and point it to the SIP device.
Now after hearing all of that I can give you the name of that wireless conference phone which meets all the requirements that you asked for, but it would be up to you and your vendor to get it working properly on the Mitel 5000 as I have only tried to make it work on the Mitel 3300; although it should be easier on the 5000.
Revolabs FLX Conference Phone <--- They say it works with Mitel, but they don't have any documentation to make it work and their tech support wasn't much help other than showing me how to get the logs out of the phone.
Thanks,
TE