You can either keep a jar and tape the chart onto the jar, or you could keep the chart on your computer and deposit the money into your savings account. You could even set a reminder every week on your phone.
We are on week 7 of this year. I just found out about this challenge, so to catch up I saved $28 today. Are you taking part in the challenge? If so, let me know how your savings are doing. I'll be posting my progress every week as a reminder and for motivation.