Ask HN: what product to build when NO FEE is available to transfer money.

If you could transfer money with no fee at all, what service or product would you build?<p>Creditcard has around 2% of fee, paypal 6%, Bitcoin around 0.0001 BTC, and so on.....<p>What if it NO FEE is needed, which product could we build on top of it?<p>IOTA, the new altcoin, does that. Just wondering what we can build on top of it.