I could be wrong, but I think you're talking about two different things.
John on Man Cave Meals used to use a Maverick ET-85 thermometer, which is not an instant-read thermometer, but a leave-in probe unit that happens to have two sensors on one probe: one sensor reads internal meat temp and one is for ambient pit temp. (I have the same model). More recently he did a review of the Maverick ET-732 which is basically the same thermometer except it uses two separate probes to measure internal and pit temperatures and has a wireless transmitter.
The Maverick PT-100 is an instant-read thermometer comparable to the Thermapen -- neither of which is a leave-in reader.
Does that fit your breakdown?
~ Scott ~
Blue Weber Performer + Craycort CI • Brick Red Weber One-Touch Platinum • Weber 26.75 Kettle • Akorn Kamado • ET 732 • Record-crushing ORANGE Thermapen • UDS In Progress