I know there is someone here that can make up this counter. I'll keep bumping until I find him/her.
Most counters already have a place for the costs savings. You input the costs per day and then the thing calc total costs. So the EXACT same algorithm/code can be used for the tar and CO (just change the wording).
Input: Date quit, cigs per day, grams Tar per day*, grams CO per day*
* grams (Tar,CO) per cig can be found by googling your brand - then just multiply the g/cigs x cigs/day.
Example for me:
34 days smoke free
1,360 cigarettes avoided
19.6 grams of Tar avoided (19,600 mg)
16.8 grams of CO avoided (16,800 mg)