I'm using QT for the user interface stuff along with a bunch of XML for module documentation and configuration. The main application is done in C/C++, but the configuration is manipulated with Python. JUCE is alright; I use a modified version of MIOS Studio 2 for analyzing communication with the Harmonizers. It's great for hacking stuff together, but I just don't like the way JUCE apps look on screen.
At this point, I don't have any interest in audio directly on/from a tablet. Everything I have done with audio has been on the Motorola 56k series chips (pardon me, I'm dating myself, it's now called the "Freescale Symphony"…) or the Blackfin.