Have had this installed in my dads car for over six months and it's been great. Only complaint, the screen could be a bit brighter for those really sunny days, it's still legible in direct sunlight so not too bad.
Tyre pressure can be set to PSI or BAR.
It has audible warnings if tyre pressure drops too low and this can be adjusted in the menu.
The main unit has a built in battery which can be charged via the solar panel or micro USB. My dad charges it via micro USB about every 4 weeks as his is placed in the centre console and doesn't get any direct sunlight. Here's a pic
The external sensors have replaceable 3v 1632 lithium batterries, haven't needed to replace them yet as it's only been six months.
Bang Good. Great postage. Expect to see it just in time for Xmas