At least two unitary states have a second chamber in which the units (departments, provinces) have equal numbers of representatives, regardless of population: Bolivia ((I would have provided a link, but senado.bo returns an error, “This Account Has Been Suspended”!)), and the Dominican Republic.
While the logic for equality of unit representation in federal systems is clear, the logic for the same organizing principle in a unitary state is much less so.
However, aside from making that observation, the real purpose of this planting is to ask the readership if anyone knows of other examples of unitary states that have second-chamber equality. These are the only two I can think of.
A further purpose is to observe that the French Senate is in the process of a major reorganization that has begun in 2011 (but it is not a case of equal representation of units).