Currently Min/Max/threshold value that can be set in several widgets (gauge, bar and indicator fields in item history and top hosts widgets)  have to be set to a fixed number. This works well with percentages as there we know the min/max values, but with other values you don't when the widget is used for dynamic purposes (host/item selection)

I think allowing expression macro's in the min/max/threshold fields would make those widgets much more usable in dynamic in uses.