The SysQueryRangeUtil class is just the great enhancement to the AOT queries made in AX 2009. It is possible now to specify a range on the AOT query with the value taken from a method's return. The requirements for such range method are quite simple: the method should be static, return string, be a member of the SysQueryRangeUtil class and not be related on the data fetched by the query.
There are quite a lot of useful methods on the SysQueryRangeUtil class available out of the box, like currentEmployeeId() - returns current employee ID, dayRange() - allows to specify date interval around current date, etc. And it is possible to add a new custom method to this class as well.