touchOSC on android
Using touchosc to control Ardour is possible. Here is a touchosc map to try out in ardour 5.1 or newer. www.ovenwerks.net/control/ardour1.touchosc
TouchOSC and the above map require some settings.
In Ardour: enable OSC in Control Surfaces and open the gui. Set port to manual and set the port touchosc will receive feedback on. (the default 8000 is fine) This map likes banksize to be 8 and gain to be position. The default for strip_types will work fine, but set it as you like. It is a good idea after setting things to click the Clear OSC devices button.
On your tablet open a browser and download the above file so it ends up in downloads. Start touchOSC and click the OSC bar. Set Host to the ip of your Ardour computer, Port to send to is 3819, and the receive port is 8000 (from above). zeroconf can be ignored. Then hit the back key and select Layout. Select Add from file and look for the Downloads directory where you downloaded the file above to. Select the file and then look for it's name in the list and click it. Now hit Done and the layout should load.
In the bottom right corner there is a connect button. Press this slowly and release. you should find the first 8 tracks listed accross the top followed by the name of the current session. On the right side there is a group of controls for whichever track is selected (the same track as the editor mixer). This track may not be one of the 8 on the left. touching one of the red squares under a track name will select that track so it can be adjusted. There is trim level and pan as well as the named buttons. on the bottom you will find transport controls.
In the middle there is a big open space to fill with more buttons for editing operations transport movement marking or what have you.
caveats: The faders/sliders are not nice, they jump to where you first touch. The buttons seem to need a real press, not a tap. touchosc does not know how to do string values so none of the Menu Actions are accessible as such. Touchosc can only do single parameter commands making plugin control impossible.
On the plus side in comparison to Control which I already wrote about, touchosc allows selecting a file from the tablet's file system, Control's layout download times out quickly. Touchosc seems to handle more traffic a bit better. The font size can be set too. Control can send strings or multi parameter commands such as select next/previous track.
The best remote control experience on a tablet I have had was with Open Stage Control which does about everything/has nice faders/pots and handles the most traffic. However it is harder to set up as it has to run as a server on the ardour machine with chrome on the tablet.
I do not know what most people would find useful for a tablet control surface. I do not think I would like to do mixes with it (adding faders for the whole bank is possible) as the faders do not really allow fine adjustment. However it is good for remote starting, record arming etc.