Image via Yanko Design
There are a few products out there already that filter water in the bottle so you can have clean water while on the go, without any bulky filters.
This concept design for easy water filtration could be a favorite among french press users.
Pretty simple to use, fill the BPA free bottle with tap water, insert the filtration press and slowly push down. I don't see any reason why it wouldn't work but there are a few quirks. The filtering mechanism seems quite large, in fact it seems to occupy a lot of volume inside the bottle. As "fun" as it might be to press my own water, I'd have to refill it constantly.
That's definitely true, but for a quick sip while out walking in the city when you're avoiding plastic bottles, or even while hiking, this could be a pretty compact, good design.
Via Yanko Design
More on Filtered Water Bottles:
Back to the Tap: Filtered Water Bottle
Brita Water Filter Ad Campaign Provokes Strong Reactions
Take Filtered Water With You
Reuse Your Disposable Brita Filter