one has to ask the pools if this transaction would be included in the next block.
The thing is, the pools aren't going to promise you that the transaction will be included in the block. Because the next moment a block could come along with a conflicting transaction (the attacker might have prepared such a block) and then they aren't going to keep working on a block that will potentially end up as an orphan. After all, 50 BTC are at risk here.
We only need to know it a pool would add it, if this certain pool would mine the next block. So an attacker would have to invest some 7000 Thashes (at current difficulty) to double spend 1BTC. And it is not easy to prepare such a block, because one has to be faster than the rest of the network (currently at some 11 Thashes/s).
I am only suggesting to use this for your 1BTC payment at the local restaurant or other small amounts. For buying a car one still would wait for some confirmations.
So the best you can get is "we received your transaction". And you can pretty much do that already: Just open a connection to the big pools and listen for the "inv" message with the hash of your transaction. If you see it, the pool received it.
Interesting idea. But you still would not know if the pool would
include the transaction in the next block. This is the information to be known. If the lets say 3 big pool would include it in the next block, chances are very high that it will get included. Keep in mind that I am still only talking about those small 1BTC payments.
ButI doubt that the direct pool connection would work, because I doubt that those pools would accept millions of connections. So I guess a simple transaction check URL at the pools would be better.