What I don't see in the DashCommand app is the ability to input custom codes to get information out of the 4R100 transmission. However, purchasing ScanXL will allow you to use the Windows version with custom codes... Apps have been available since Palm devices became popular in the 90's but sometimes a dedicated appliance has better usability than a multi-function device.
There are cheaper alternatives than the ScanGauge, but this tool is easy to deploy in stock form, read data when driving and customizable for manufacturer specific codes. I do not have financial stake in this company and actually sold off my gauge after selling my 2005 Ford and finding that my 2015 Ram had the parameters I wanted available on the OEM dash display. The person that bought mine got the benefit of having all custom codes already programmed for his vehicle.
The OP will need to choose an app, vehicle power cord and some type of vehicle mount if he wishes to use his phone for constant parameter display. This may limit him using his phone for navigation and hands-free calling while using the OBDII app, so that is another consideration.