I've found this milk jug to be really helpful in getting consistently well steamed milk for latte art. The temperature sensor on the side allows you to end steaming at exactly the right time (typically 65 degrees), no batteries needed.
Fits enough milk for a 350-380ml cup, with a 36-44ml espresso shot.
For anyone wanting to work on their latte art skills, I'd recommend checking out Lance Hedrick's and Emilee Bryant's milk steaming and latte art tutorials, they're both former latte art world champions and go into a lot more detail than some of the other tutorials I've seen.
Jug is too big imho. As for temp - just feel the side of the jug with your hand and you'll get used to the sweet spot.