These activities are ranked in order of difficulty. I would humbly suggest that you try to use this list as a way of assessing your own skill, from beginner to perambulatory veteran.
1-Listen to music
Obviously, this is the simplest achievement. So long as you aren't trying to concentrate on too difficult a pattern and the music isn't too loud, I expect you could do this while you were newly learning. The only real hazard is subconsciously trying to knit along to the beat of the music. No thrash metal, and no miming along lest you get to excited and use your needles as stand-in microphones.
This is subdivided into:
The general rule is to use a straw so you don't have to let go of your knitting, but it's very difficult to maintain a rhythm while you lean over for a sip. Other hazards include wet knitting, cold tea and drunk knitting. I've not seen any good examples of drunk knitting yet, although drop-stitch always looks like it was done by a wino. Please send me any pictures if you have them.
3-Watch a film
To watch a film and knit at the same time divides so many of your senses! Your eyes and attention are flicking between two things so quickly! Scarves and any repeating patterns are more easily done while completing this activity. Themed knitting is a possibility, allowing you to have a LOTR marathon and knit a shawl, or whip up some Harry Potter scarves. I don't recommend knitting in the cinema as the needles may be hampered by the arm rests (never mind the annoying clicking).
This is initially difficult due to the sheer mechanics. You can try balancing the book on your knees or on a cushion, but how do you keep the pages open? Once you've mastered that, the secondary difficulty emanates from the fact that reading and knitting seem to both use the same part of your brain, meaning you can easily flip flop between the two but will have great difficulty giving both simutaneous attention. Audiobooks seem a far wiser option, and you will only give yourself a headache trying to read something on a computer screen.
You are highly unlikely to ever need or want to walk and knit at the same time, especially outdoors, but emergency situations happen and you need to be prepared. I recommend placing the wool and the bulk of the project in a bag, putting your hands through the bag handles and knitting with the needles floating on top. Try practicing at home, but understand you can't anticipate all the confused onlookers in a real life situation, nor be able to open doors with any ease. If you are knitting in public to try to have alone time, know this: men who think they are funny will request items. One man wanted a lace jacket from me.
If knitting is only a hobby, you are less likely to encounter EXTREME KNITTING SITUATIONS but the career knitters and aspiring shop owners like myself will find themselves in bizarre predicaments from time to time. Feel free to suggest other achievements I have not yet accomplished!