Touchdaw is a great value, and a great app too. It's a Mackie controller on your Android device that connects to your DAW over WiFi (and even over USB and BlueTooth if you are an "advanced user"). Meaning you can e.g. sit at the piano and control your DAW, including faders, automation, transport, etc. It works over the same infrastructure as the remote iPad app for Logic X.
If you are running your DAW in Windows you have to first install Apple's Bonjour, Tobbias Erichsen's free rtpMIDI and configure stuff that isn't native, in addition to dealing with Wifi, Firewall and TCP/IP issues. It might or might not drive you mad. Once you get over the hump, it runs OK. TouchDaw itself runs just fine, it's just that on Windows the protocol stack is a bit fragile, so it's more appropriate to say it runs OK.
On a mac it's much much easier, and it runs very well. This is because OS X has Network MIDI well integrated. It's also much better at recovery from disconnects and other inevitables that on the Windows side can require restarting stuff.
If you are already running a hardware control surface, there are different ways to mate TouchDAW with it. In Logic it's relatively easy to run the two in parallel. In Cubase the tendency is to spread channels between control surfaces, so tracks 1-8 might be on your hardware faders, with 9-16 on TouchDAW, which is not exactly desirable.
This is a fantastic app for advanced users to add to their setup. There are great rewards to be had, but also lots of potential pitfalls. There is a free version of TouchDAW that can be downloaded to check how well you will manage to get it running. Definitely start there.