Well, I trained mage for awhile by alching and I gotta say that I watched a hell of a lot of youtube gameplay walkthroughs (SSoHPKC puts out really good gameplay commentaries, and like 6 videos a day) but you could walk television or something too. Also, don't rule out stun alching if you want to save some time, though it requires attention.
I cant remember the last time I did alching by hand, probably 06'. I used to just deal with the boredom and talk to other people in the fletching guild in Yanille back in the day.
Same except I minimize the rs screen to the point where all I can see is the high alch portion of the magic tab. Then I just click while watching youtube
I go out and have a life cus I only bot alching If I was doing it legit though I'd probably move the rs window over and just watch shows or movies on my computer at the same time.