There must be a bazillion tea-infuser devices on the market, and among them is the Blomus Tea Stick ($20). The design is modern and the idea is good. You press the stick's plunger, insert the other end into your loose tea so it fills the stick's container, then release the plunger to neatly contain the tea.
It works well if the loose tea you're using is the right size. Big leaves and chunks won't fit.
When it comes to infusing, the tea stick is pretty tall, so it's fine if you drink your tea in a mug. If you're using a short, fat teacup, this isn't going to work so well.
My pet peeve when brewing tea is that I don't want bits and pieces in my tea—I want a clear liquid without bits of leaves floating on top and gritty bits falling to the bottom. The tea stick doesn't spew bits the way my poorly-designed tea ball did, but small bits escape through the holes.
I like the way this tea stick looks, but I'm less enthusiastic about its function. With some teas—the ones that had pieces just the right size—it worked perfectly. With other teas with larger or smaller bits, it was much less successful.
Disclaimer: Testing samples were provided to Serious Eats.