I wouldn't worry. Our DS was probably about the same at that age. Our DD, the same as yours, can say the name of her brother, rabbit (her favourite toy), yes, no, pull, and ball. Oh, and she's just learned "pooey" :-) But she understands a huge amount.
My 21 month old is the same. He can say mum , purple (randomly!) mmmmmoon, car. That is all. I spoke to the health visitor who said this is common, so they will not normally do anything until the 2 year check. Unless you think your child has hearing problem and lacks the ability to hear the sounds and therefore say them, they will arrange a hearing test. My DS, like yours, understands a lot of what I say and points etc, so I am sure it will only be a matter of time before they talk more!