You could do that a few ways.
Use the username or users group in the RQL query for the data points.
Do an RQL query to get a list of unique Device Names the users has permissions for and then use those in the drop down. It would default to the first one but if they had permissions for more then one they could still use a selector.
Put all the data points in a point hierarchy folder that matches the username and use the username in a point hierarchy query.
There are probably more ways but I think this should give you some ideas. This is probably something we could put some examples together on in the coming weeks.