If you want to send bitcoins fast at the cheapest possible fee but don't have the time to monitor https://jochen-hoenicke.de/queue/#0,24h because you're on the go or doing something else, a mempool notifier would be helpful.
What's the point of trying to see what the mempool is empty to send a transaction, just send it now with a lowe fee and when the mempool is empty it will be confirmed, you don't have to wait and send it exactly at that time.
Besides, how can you send something fast when you're waiting for something else, you might be sending it fast from that moment on but it will be pretty slow since now.
My plan was to wait for the mempool size to drop below 10MB but the problem is I'll be busy in the next few hours and I won't be able to monitor. A notification message would help me send on time before the network becomes congested again.
Just as I was saying, send it now and it will be confirmed just as fast
There are times when 2-3 blocks get mined in a minute two, so by the time you receive your alert and finally manage to send the transaction because of luck you might have to wait 30-40 minutes for the next block so the alert will be useless as the mempool will be clogged again by then..
