@Michael_Soprano pass it in via mbox parameter - 2 options:
1) Save it to the user profile, then you only have to set it on the first request after login, but you need to ensure to also set it to false, when they log out as the true value will persist to future visits.
alloy("sendEvent", {
data: {
__adobe: {
target: {
"profile.isLoggedIn": "true"
}
}
}
});
2) If you don't want it to be on the profile, you simply set it without 'profile.', but you'll then have to set it on every request while they are logged in.
If your login happens on a certain URL/sub-domain, you could create a profile script that checks the URL and then set the value to either true or false.
Once that's done you have it available as @bjoern__koth described.