Strictly speaking, the Bladed Belt is a Wondrous Item. It happens to be able to transform into a weapon on command, and can even be enchanted like a weapon, but it is still a wondrous item. You can expect major table variation with this one.
Good question. I'd allow it in home games.
As DeathlessOne says, the Bladed Belt isn't listed as a weapon so it doesn't qualify for your Arcane Bond.
If you wanted the belt for its ability to transform into a variety of weapons, you can get a somewhat similar functionality by adding the Transformative special ability to your bonded weapon. Unlike the Bladed Belt you are locked into a single "handedness," but at the same time you aren't limited to slashing or piercing forms.
A more unusual option for versatility is the Fighter's Fork. You can brace it, throw it as a trident, throw it as a javelin, shorten it until it is a light weapon, wield it as a one-handed weapon, wield it as a two-handed weapon without reach, or lengthen it into a two-handed reach weapon. That's pretty versatile. Especially since any feats that apply to tridents will work in any of its forms. It qualifies for an Arcane Bond since it is listed as a weapon.