We have a need for equipment to post status updates to salesforce. Unfortunately the equipment lives on a secure network that will not allow return communication The methods I see all require a request for an auth token and then use that token to post to the rest method. Is there a way to do this in one shot just straight post to the rest method with a preset token or a combo password api token?
Best option - generate your access token outside of your app and keep it alive via another process (see Customer.io: webhook access_token update for details). This will be equivalent to your "preset token" idea. Your app can then use the access token in a one-shot manner.
Another option is to publish your code to force.com and allow unauthenticated access from a platform perspective. You could then read a token of your own format to authorize calls - see the answer in Rest API call to Salesforce from site - one call only , it illustrates this. This is NOT a best practice and it's very risky to implement because of a wide attack surface. Even an amateur attacker working with well-known exploit techniques can achieve quite a bit of success if the implementation doesn't consider a long list of security nuances when rolling something like this.