I think this is a good idea! The Yahoo Finance app has this feature.
You can click on the basic graph on a Stocks page, and it will pull up an more advanced graph, where you can add indicators, see volume, compare with other stocks, change between 1 day, 5 day, YTD, etc.
As you have said, you can also rotate your phone to make even better use of this feature. It is very useful to see a lot of detail when on the go, if you canβt get to a laptop. Or, if youβre just interested to see the charts of different stocks!