Is there an API trust.salesforce.com. status?
Is there a public API available to access the trust.salesforce.com information?
(or)
Is it possible to set up monitors to get automatic updates if there are performance issues/degradation with a particular instance?
There is a public facing API for trust.salesforce.com. status:
https://api.status.salesforce.com/v1/docs/
You can make a request such as the following to obtain parseable json with status information, degradation, outage, etc, info:
$ curl https://api.status.salesforce.com/v1/instances/NA48/status
You can also install SalesforceA for either Android or iOS to get access to the latest status, view user information, unlock, freeze/unfreeze, activate/deactivate, reset passwords, etc, from your mobile phone. Salesforce just released a native port of the Android client last week which is nice and fast, too.