It is impossible. Some sensors have FSK modulation.
But even for ASK/OOK modulation there are many different protocols. Actually all senors have unique protocols and just some of them are similar to another and can be decoded to some degree.
For example, there are descriptions of some of these protocols:
http://www.osengr.org/WxShield/Download ... tocols.pdf
And you cannot easily see the signal because you don't know when you get it. You receive a lot of noise and the real problem is to distinguish signal from noise. Without any knowledge about the expected signal you cannot do it.
Look at another my project https://github.com/alex-konshin/gpio-ts
. This is a driver that does raw filtering of input from RF receiver and makes more easy reading and decoding such signals. It also reduces the load on system because it gives your application only "good" sequences that meet some criteria. Application reads the sequence as file of 4-byte values. My project that receives data from sensors may use this driver (and I actually use it in my own setup at home).