API / hook for signup and sales etc

I know PayPal have their IPN, and Stripe have their webhooks, (ClickBank, Authorize.net etc, no idea) But I was wondering if there are single ‘hooks’ within the program that is fired when:

A) A customer starts a trial subscription
B) A paid subscription starts
C) A subscription is cancelled
D) A single product is purchased
E) A single product is refunded

In short, I am developing an affiliate tracking script. (Can’t afford the likes of IDevAffiliate !) Getting notification of clicks to sales page is easy; that is a simple javascript source that calls a PERL script to log the visit, (and a localStorage flag so as not to trigger multiple ‘clickthrough’ when people revisit the same sales page)

At present, I’ve been looking at integrating the Stripe webhooks / endpoints. This morn, I realised that the subscription / cancel subs would work FOR ME and what I was selling … but wouldn’t integrate to someone running a subsscription on their own site. (For a while, I considered a “repeater” script that would simply sent the Stripe data to me, and I would then pass on verbatim to the client’s machine … but that may cause ‘security’’ headaches!) So I’m now looking at using S2 for clients as the backend if they want to run subscriptions.

**** That said, I’m also a little concerned that there appears to me no recent activity - pre-sales email contact is now not available - so I’m wondering if the plugin is still active.**

Sorry it’s a bit of a ramble, but I wanted to explain the context of what I will be using the keys for.