Regarding bicycle computers with altimeter and inclinometer functions....

1. In addition to a SigmaSports BC1200 with Cadence that uses wired pick-ups
on both tandems, Debbie has an Avocet Vertech II that she attaches to her
handlebars to keep track of our ascents, descents, and the weather:
http://www.avocet.com/vertechpages/vertechalpin.html

2. Always being curious about the grade of various climbs I came across the
wireless CicloMaster CM414 Alti last year and it has proven to be a really
neat computer that provides many useful features -- like an adjustable trip
odometer and forward/backward scrolling -- and more data capture and logging
features than I've ever seen available from a bicycle computer:
http://tinyurl.com/6ap (or go right to the CM414 by visiting:
http://www.ciclosport.de/eng/html/katalog/cm414a.htm) It runs off a wireless
pick-up from the front wheel of our tandems.

3. I recently tried out the Specialized Speed Zone Pro Classic and while it
too provided percent grade and vertical feet gained along with most other
cyclo-computer functions, it was hard to scroll through the data while you
were on the bike and offered no where near as many other features that were
available from the Ciclosport. http://tinyurl.com/6apm

Summary:

The CicloMaster CM414 Alti is really slick, very accurate and has more ways
to look at data than anyone needs; I love it. It's bit on the pricey side,
comes with a wireless transmitter and accessories are also bit on the
expensive side. Altimeter function is accurate but altitude gained will
seem to come up a bit short due to the way the computer collects the data,
i.e., sampling rate will result in minor gains and losses being ignored.
However, you'll get credit and see all your "Max" effort data at the end of
the ride. You really need to read the instructions carefully. Don't have
the PC interface or software for post-ride analysis so I can't comment on
it.

The Specialized Speed Zone Pro Classic at $99 comes up short on features and
usability. You must scroll through 12 functions to see what you want and if
you miss something, go around again. Altimeter doesn't record descents, nor
does it capture max, etc... Same with inclinometer: shows real-time (and is
a bit generous compared to CicloMaster) but does not capture max up, max down
or average. Made by same company as CicloMaster and uses the same wireless
pick-up (in fact, I ran both the Ciclosport & Speed Zone computers off of
the CicloMaster's pick-up at the same time). After conducting my
side-by-side comparison I sent the Speed Zone back to Specialized.

The Vertech II is not a cycling computer; rather, it was designed for
mountain climbers, skiers and hikers. It is the most accurate of the three
altimeters but subject to errors/needs recalibration as the barometric
pressure changes. However, the altimeter functions are really nice and,
when used in conjunction with a regular cyclo-computer it gives you some
other interesting data to use.

If I could only have one, it would be the CicloMaster. However, since I
already had the Vertech II and the SigmaSports computers it's really nice to
have all three. The SigmaSports is hardwired to the rear wheel and has
different re-set features than the CicloMaster which is nice, plus it allows
Debbie to watch our cadence. The Vertech has allowed Debbie to keep an eye
on our altitude, vert. feet gained and although it doesn't have an
inclinometer to tell her what the grade it it does indicate if we are
gaining or losing altitude. The Vertech's altimeter function also allows me
to sanity check the CicloMaster's current altitude (they both seem to stay in
sync. even when the weather changes).

Bottom Line: The altimeter functions are not precise in the truest sense of the word. However, the "vert. feet gained" is what most folks are interested in and any of these devices will give you that data. If it's off by 10% (+/-) it'll always be off by 10% (+/-) so they will still provide you with relatively comparable data for different rides, i.e.,Joe's Mountain Ride netted you 5,600 vert feet and Col de Bubba netted your 7,600 vert. and the difference was an approximate difference of 2,000 vert ft.

If you want something more accurate than that get a compact GPS unit.