Just build a workflow that will wait for a specific date. Then it will go into a loop where it starts by checking if a field holds the value "False". If it is false then it will wait 24 hours and then check again to see if the field is still "False". This loop will continue until the filed is set to "True" and then it will terminate.
But - if the item in the list that caused this workflow to start, is changed - then there will NOT be initiated another workflow. Looks like I can only have on running workflow for each item in the list. Is that correct or am I missing something?