Hi I've just brought a Timex one for £40 from B&Q it has an outdoor sensor with temperature and humidity.As for eating batteries I dont know yet ,but the main unit takes 2 AAAs and the outdoor another 2 AAA's.It measures barometeric pressure.But the outside sensor will only measure down to -4 temperature wise.I consider it more of a toy myself,so I guess you'll have go for what you need.
Jason.