Hello,
I have an above average knowledge about Bitcoin network, but I lack some advanced understanding as how transaction works. So I hope you can clear this that is in my mind for some time.
I know that it is possible to purge a transaction nullifying it, for example if you sent a transaction with a low fee it will remain unconfirmed for some time and it gives you the opportunity to purge it so it will be canceled and your balance will be fully restored in your wallet.
My doubt resides on it, considering that my previous statement is true (please correct it if it's not), is it possible to set a server with automated bots that will be checking the mempool/network for unauthorized transactions comming from your wallet and auto purge them to prevent it?
If what I said is not possible by any reason, please explain and if you have the knowledge, please try to answer this as well: is there any coin that allows it? I mean, it won't hurt the network as it's only for unconfirmed transactions.
You can't purge your transactions. It will simply disappear from the mempool after being in limbo for a while. It happens when you pay too low of a transaction fee.
If you're worried about your Bitcoins being compromised, just take every step you can to secure them. It's harder to steal them than you probably think for as long as you follow basic security steps.