@Andrew Watson
You can set cell level acls via the HBase shell or via HBase's Java API. This type of policy is not exposed or controlled via Ranger.
If possible, I would implement row level policies in a client-side application, as HBase's cell ACLs are expensive (additional metadata must be stored and read with every cell).
My favorite solution is to create a Phoenix View that exposes only specific rows. As noted above, your client-side app would have to decide whether to allow access to a given view.