I wonder what counts as a credit monitoring service. Can I choose what service I use? ...Can I monitor it myself?
1) It must be a third party service that you have entered into a business arrangement with, where the arrangement in clear and specific terms provides you with credit monitoring.
2) It must hold up in a court of law if challenged.
That second one is the anti-loophole provision of law, and protects against the kind of loopholes people try to find to get around the clear intent of the requirement.
You can choose to use any service that would hold up in a court of law. There are no clear answers on whether "any" service would. Time established, diversity of customers, active or inactive business, frequency of credit report inspection; all could be factors in a judicial evaluation of whether you complied with the terms or not. Capital One? Yes, they plausibly do offer credit monitoring as a service. Joe Bloe's Credit Woes? Entirely possible, if they've been around a while and can demonstrate that they pull credit reports on a regular basis and audit them in some manner.
Can you monitor it yourself? Only if you already operate a credit monitoring business. Otherwise, it'll fail the plausible test, and you lose your $125 + lawyer fees + risk angering a judge.