Satoshi built Bitcoin to be a decentralized network. Some of the original recommendations (such as waiting for 6 confirmations) relied on statistics that related to level of decentralization.
According to the math on page 9 of the whitepaper there is less than a 0.1% chance of successful a double spending attack if a rogue miner controls 10% of the network hash rate and the recipient waits for 5 confirmations. However if a rogue miner controls 45% of the network hash rate you would have to wait for 340 confirmations to reach the same level of confidence (less than 0.1% chance) of a double spend not occurring.
Are there any tools that automatically monitor the hashrate of the major pools and dynamically use that data to change the number of confirmations merchants request? My intended use case would kick in for large purchases when/if a major pool went down, giving another pool (at least temporarily) a very large percentage of the network hash rate.