Product review (4 stars): Decent cheap thermometer.  Has probe for external power.
So got this about a week ago.  Not sure about how correct the outside temp is.  The temp on the actual device takes a while to become correct.

This has a fairly large screen, so the numbers are easy to read...but there is no back light so you won't see it in the dark.  It shows the time and the humidity on the bottom.  The devices temp on the top line and the temp of the metal bead that is at the end of a 4 foot wire.

First thing, I had to change it from C to F because I am an American....Next, I noticed that there is no way to detach the cable, so it would be a bit hard to travel with.  I also have tested the external probe by putting it in my fridge, where my fridge says it is 33 degrees, this said it was 40...but maybe it tested it from a different place.  I also left it in my car with the probe outside, in an hour the inside of my car was 107 and outside it was 104 in the shade...my car temp said 101, so that was close.  After driving a while I put the unit in the flow of air from my AC, that I know is under 70 but even after a few minutes it still said 78.  So it seems that it does give you the correct temp after a long period of time, but it is really bad at changing temps, even 20-30 minutes it not enough.  So I would feel that this gives a good idea of the temp, but not totally correct all the time.  I did get this at a deep discount because they wanted me to review it. I gave it 4 stars.  If the cable was detachable or the screen was backlit with a button or it was more accurate it would have had 5.