I have at least a dozen projects, clients, side projects, personal domains, etc., each with a TLS cert. Plus at least 5 certs for work. All of them have different expirations. Some are on Let's Encrypt without auto renew at the moment, meaning they have varying expirations less than 90 days from now.
I would love just a simple iPhone app where I can list my domains and get push notices at 30 or 7 days from expiration. Maybe I should make this myself because I've yet to find one.
http://www.site24x7.com/ has a cert monitor that does exactly what you want and more. If you have 10 domains it will run you $10/month. (Although you probably also want an uptime checker, so really it's more like 5 domains on the $10/month plan.)
Sure, that's fine for an individual, but what about for a business? If the person who has an entry in his or her calendar leaves and forgets to remind someone else, what happens then?
We have a shared calendar in the business with all this stuff on and there's also a reminder that crops up in the order system (Mainly because monies are due to change hands again rather than the ssl is about to go pop)
I would love just a simple iPhone app where I can list my domains and get push notices at 30 or 7 days from expiration. Maybe I should make this myself because I've yet to find one.