VDO makes cyclocomputers with fairly accurate altitude measurement, and it comes in wired and wireless (M4 WL) versions. I recall a tourist (from CGOAB) using a previous generation VDO M4 crossing the Americas. VDOs don't seem to be sold in USA, but Wiggle and MEC sell them. I've considered buying one but it's hard to justify with 2-3 perfectly functioning Cateyes on hand.

http://www.wiggle.co.uk/vdo-m4-wl-wi...ycle-computer/

http://www.cycleparts.de/en/products/m4.html