Gosh, I'm getting very tempted to buy a slow cooker! Plum, do you reckon it's a Gi friendly idea?
(sorry I have rambled, my brain is getting sleepy and non-concise!)
Hm, I'd say yes if you already have GI-friendly stews/casseroles etc. that you like making but don't want to be tied to the house while they are cooking (def look for one with a timer that switches to 'keep warm' when done if you are away all day). You can add tinned beans to the slow cooker, not just dried, just be aware that they'll eventually break up with long cooking.
I usually remove or reduce the proportions of less friendly things, so I might now make a stew and throw in some pearl barley towards the end instead of potatoes, or use sweet potatoes, or for things like the split pea soup I've increased the gammon a bit and will be mindful of the portions that I eat (and forego the lovely crusty bread :cry

. If I make chilli or something I'll put in more veggies, and so on. Also I already liked things like beef bourg. which just has meat and veggies, no potatoes/starch (unless you count wine....).
I have to say though that I couldn't personally get a lot of use out of the slow cooker if I were living on my own - because I am not a morning person!!! You do have to either get things going in the morning (which The Husband does, bless him) or else cook them overnight (but this only works if you are not the type to be awoken by smells wafting through the house, which I am).
Left to my own devices I'm personally more suited to a pressure cooker and making stews etc. quickly at the very last minute (but if you're trying to watch fat be mindful that you have to add oil to anything you cook with beans, lest the skins clog the vent and explode everything everywhere).