On-call software
Four things have to work. Everything else is a preference.
1. A rotation somebody will actually maintain
The schedule is only as good as the last time it was edited. What makes one maintainable is boring: layers you can reason about, overrides that take ten seconds when somebody swaps a weekend, and a calendar that shows who is on rather than a rule you have to evaluate in your head.
The failure this prevents is the one nobody notices until it matters — a rotation with a hole in it. Acked mails the admins when a schedule stops covering the next two weeks, because an uncovered window is invisible until an alert falls into it.
2. Escalation that gives up on a person, not on the alert
One phone is not a system. The whole point of on-call software is that it waits a defined time for an acknowledgement, then tries somebody else, and keeps going. When the chain runs out it has to say so loudly rather than closing the alert quietly.
That last part is where tools differ more than you would expect. An alert nobody answered should be the loudest thing the product ever does.
3. A notification that survives a phone on silent
An on-call tool that emails you is not an on-call tool. Both mobile platforms have a way to break through do-not-disturb — critical alerts on iOS, a high-priority channel on Android — and a paging product that does not use them has misunderstood the job.
Worth testing before you rely on it: put the phone on silent, in another room, and send yourself an alert at an inconvenient hour. It is the only test that counts.
4. A record of what happened
Not for compliance. For the ordinary argument the morning after: when did it fire, who was paged, did the page arrive, when was it acknowledged, and by whom. If the tool cannot answer those from its own history, you will be reconstructing it from screenshots.
Acked writes an append-only record of every state change, and every delivery attempt with its outcome, including the failures.
What is optional
Status pages, postmortem workflows, service catalogs, incident roles, AI summaries. All real features, all worth money to somebody, none of them the reason the phone rings. If a tool is strong on those and vague on the four above, it is an incident platform that also does paging, which is a different purchase.
The pricing question, since it decides the rotation
Per-seat pricing on a pager charges you for the thing you least want to economise on. A wide rotation is how you stop the same three people carrying every night, and per-seat makes the smallest rotation the cheapest one. Teams do that math and quietly decide somebody does not need an account.
Acked is flat per month with unlimited users on every tier, including free.
When this is the wrong answer
If you need status pages your customers read, a postmortem process the tool enforces, a service catalog, or incident roles and comms templates, buy a platform that has them. You will be happier and it will be cheaper than assembling the same thing out of parts.
Acked is for the case where you looked at that platform, realised you would use one tenth of it, and could not find anything smaller that was still serious about waking people up.