I just use a spreadsheet. It's not fancy or particularly efficient, but I like how easy it is to add new columns, create graphs, add notes, etc. Flexibility beats speed for me, since it's not like the data entry takes much time anyway. (This doesn't answer your request for a "better" method, but it answers the top-level question!)
I use the Giving What We Can pledge tracker. If you take the 'Try Giving' option you might be able to access it: https://www.givingwhatwecan.org/pledge/
Yeah I have seen that as well, thanks for sharing! Do you know if you can actually share that publicly as well?
If it's possible to share I don't know how. I suspect not. It does have a summary chart that you could screenshot every once and a while: "You have donated $X and fulfilled Y% of your pledge", for one each year and one for all time.