I know these are a personal taste, some like them others dont BUT i have not seen many being used for quite some time and i dont think anyone who quit since January uses them.
Some of us oldies used them a lot, particularly at the start of our quits because it is very encouraging to see another milestone coming up soon and that alone can help keep you strong.
There are a few here:
Harry's is a good one.
This is what they work out for you (and display if you want.......)
John - Nicotine Free for One Year, 22 Hours and 55 Minutes, while extending my life expectancy 31 Days and 20 Hours, by avoiding the use of 9174 cigarettes that would have cost me Â£2,420.29.