Most banks have alert systems set up now where you can get alerts sent when the balance gets below a certain amount, when a debit card amount posts, etc. The Treasurer should not be the one to have his/her name on the debit card, but should be the one with online access to the bank account. Then have alerts sent to the treasurer's email whenever there is a charge to the card, or when the balance in the account changes, or something like that. Our rule is that you have to submit a receipt to the treasurer within a week of making a charge, or you can have your card cut off. Also, when you set up the card, make sure that it is set up in such a way so that no one can use the card to overdraw the account--sounds silly, but you used to be able to go use an ATM with a debit card and take money out of your account even if there wasn't enough money in the account. Some banks will still allow you to do that unless you specifically tell them not to.
I think if you have a safe at school and have a sign out where multiple PTO members have to be present to even GET the card, then it's ok. Like anything else money-wise, you need to have strict rules.
It certainly allows you to get things done faster.
