Bitcoin Forum

Is there anything in bitcoind RPC (or even an external service, blockchain.info etc) which would let me get an idea about how many miners have a particular transaction in their mempool? Or even some other metric of 0 confirmation transaction confidence?

You can call getblocktemplate to see if your own node is attempting to mine it in the current block.

Consider me to be uninitiated - is this relevant only if I'm a miner, or if I'm running any full node?

Pfft. If you were a miner 99% chance you've never seen a full node in your life. Any full node can call that rpc, and only full nodes can call that rpc.

Ok, understood. And if this call indicates a positive response for a given transaction, how much overall confidence does it give you about inclusion likelihood?

Anyone know about this?

I'd really like to some kind of metric about block inclusion likelihood for a given transaction.

A lot depends on the priority of the transaction, number of transactions queued etc.  Generally, if you were to calculate the priority for each transaction, that would give you a good metric showing which ones were most likely to be included sooner than others. e.g. you could say, transaction A is most likely to be included while transaction Z is least likely.  I am not sure if there are statistics about it.

It could be calculated if you were to run a full node, calculate the priority when you see a transaction, and then see how long it takes a transaction of a particular priority to be included in a block.  Doing that for a while would let you create statistics - e.g. perhaps by 20% baskets and then you could say, the top 20% are included within X time with a confidence interval of Y.  Then for each of the other baskets. 

e.g. Look for priority calculations
https://en.bitcoin.it/wiki/Transaction_fees

Blockcypher has what you need:

http://dev.blockcypher.com/#zero_confirmations

Wow, this looks awesome - many thanks :)