Any blood glucose meter works well. I know someone here recommends the NovaMax.
The AccuChek Aviva is popular because it is cat-friendly and easy to use. But test strips are pricey so shop around for the best prices. Ebay and online pharmacies are some places to buy from.
Wal Mart's Relion brand of meters are inexpensive and works well. But the test strips are only found in Wal Mart stores.
Meters with test strips widely available in many big chain and supermarket pharmacies are OneTouch (the Mini one is the most basic, I think), AccuChek, FreeStyle, and Contour.