Philos

Blurter. got mine from RS too, its preferable being battery operated & therefore I don't need to worry about invalidating my warranty or telling the insurance co that I've wired something into the fuse box.
Appearance isn't great, its purely a funtional driver aid and can easily be removed, comes with 3m of cable too. Checked accuarcy of external temp and its spot on! The inside temp will never be accurate where Blurter and I have put ours, unless you use air con all year round on the 8 o'clock 'through car' setting/vent direction.
BTW its