DIY cycle computer: the goals

Quite some time ago my CatEye Asltrale 8 got broken again. Namely, there were some problems with wires, so I decided to buy a new computer. To my surprise, it was a really difficult task...

What was I after?
- A wired bicycle computer. My experience with £100 Cateye Strada computer was a disaster. I thought that "wireless" means that I should not bother about wires. On contrary, it means that I should bother about signal. The heavy sensor-transmitter module near the pedals was always shifting a bit, it required adjustments quite often. After a few months, the computer just stopped working. Moreover, the range was barely enough to put the computer on the handlebar. It was fine for the stem, but additional 20 cm (to put it on the handlebar) created a lot of problems with the signal. It is easier to change the wires every 2-3 years that to adjust the transmitter every hour.
- Cadence. Surprisingly, there are quite a few computers with cadence. For some it is possible to buy cadence sensor as an accessory - meaning high price.
- Altimeter. Yes, it is funny to have some kind of altimeter. It cannot be perfect, but it should be better than nothing.
- Small size, reasonable battery life. There are a lot of all-in-one computers on the market that combine a GPS, cell phone, can opener, etc. In fact it means that this computer is huge, heavy and lasts a few hours on batteries - not an option for cycle tourism.
- Temperature. Knowing the temperature is also interesting. A very rate function.
- Reasonable price. Yes, I am stingy.

The only option that comes closer is Sigma BC 16.12 16, but it does not offer altimeter + the cadence sensor should be bought separately...

After some hesitations, I decided to make my own computer using ATmega (raw Arduino). A few options found in the internet were not encouraging...

http://blog.arduino.cc/2013/08/28/diy-bicycle-computer-with-arduino/
http://www.instructables.com/id/Arduino-Bike-Speedometer/
http://www.instructables.com/id/Wireless-Altoids-Cycle-Computer/
http://www.lucidtronix.com/tutorials/13

Enormous bricks on the handlebar that are obviously neither water-, not vibration-proof. Moreover, these must consume handfuls of batteries. Not an option. A few more examples below were much more promising:

https://github.com/rhn/jazda
https://github.com/carmolim/cycloduino

But these lacked some functionality and were to difficult for me to understand. In fact, building this stuff is more interesting than using...