To Nick_Pyner
You can get a suitable temp sensor for about $5. A pressure sensor may cost a little more.
For reasons I don't understand, it can cost about $100 to put an Arduino on WifI. If you can avoid doing that, the whole deal could cost less than $50
If your phone can see anything of note here
it is looking at the output from an Arduino.
thanks for the comments. I will check it out. I also have no idea why the Arduino unit costs crazy dollars. Keep'n the man down!