Anything "aviation" costs a lot more.
At Friedrichshafen (AERO 2010) I saw, on the Jeppesen stand, a firm showing some pretty slick tablet computers. 2900 euros. It turns out you can buy the same device for about 50% of that, from the company importing them from the Far East - if you do not mention "aviation".
Yet these are all portable devices so certification is not an issue.
Regarding CO, I use a BW Gasalert device which is really good - it picks up exhaust of the plane which landed before me, sucked in through the heater - but it cost a helluva lot more... about £350, when I bought it a few years ago.
A lot of stuff has come down. Blood oxygen meters too; I paid over £300 for mine and now they are below £100. What the accuracy or battery life is like may be a different story...