Drip lines would be better. Google "drip irrigation for window boxes". Lots of suppliers and options.
A soaker hose will drown your plants, I second the drip irrigation properly set up the will save on a water bill.
Here's one that would be pretty easy to either make or find in a store. Wishing you the best.
I wonder if a drip irrigation set would be better than a soaker hose for your window boxes? Here is a set I quickly found. (click to go to shopping link)
Instead of soaker hoses, I would look into a drip irrigation system. It is easy to install and the small rubber hose is not very noticable. Lowe's or HOme Depot have all of the parts to build your own. It is not hard to do. Then you can put the system on a timer and water on a schedule without any work on your part. I used this for all of my hanging pots on my porch. So every morning at 5:30 the plants were watered automatically for 3 minutes. It works like a charm.