The solution is to analyze the transaction and determine how likely the transaction is going to confirm in the a few blocks. Generally you should look at the size of the transaction (a large transaction may be less likely to get into a block), the transaction fee per byte, the outputs (for dust outputs), whether the inputs are confirmed, and whether it signals Opt-in RBF. By examining these, you should be able to decide whether you think that transaction will confirm and whether you should accept it. If it opts-into RBF or spends unconfirmed inputs, you should wait for at least 1 confirmation as that transaction could be replaced.
This is exactly what I am trying to do, not just analyzing the Nodes in real time, also analyzing the input's "history",
But it seems that not too much change from this days :
https://bitcointalk.org/index.php?topic=3441.msg48365#msg48365 Maybe its too complicated, or maybe there is not enough double spend transaction out there? what is sure is that the "Double spend" issue is one of the biggest barriers for Bitcoin to be adopted by "regular" payments companies/Financial institutions, Its 10 minutes Bitcoin against 0.08 mil second Visa.. they are really afraid from it as far as I spoke with some of them.
Someone know where I can find "All time" statistics about double spend transactions?
Simple solution would be to wait for confirmations (at least 2)
I afraid this is not enough, we need to wait for 4-5 to be sure, and that's gonna take 5-6 minutes at least, that's a lot of time for a digital money,
Maybe some Block-scale will solve that during the years too.