btw: l love intervals 
and use it more and more and because mywhoosh and garmin i also broken since some weeks my indoor rides dont count any more on garmin:
how about adding something like training readiness status? because we should have all information like health and fitness (form,..)& last activities..?
to clarify: calculation of an own status independent from and imported field…
also training status (peeking, unproductive..) would be a similar thing
Training Readiness numbers are useless and market driven made-up metrics.
This platform logs your training and has data for, best case, about 10% (for most of us) of your time. What’s happening during those other 90% has a big impact on recovery, just as nutrition does, and influences heavily what your readiness is.
HRV and daily subjective scores give more insight but are difficult to transfer to a ‘number’.
Use common sense to have an idea what you can handle today. Even then you will have days where you need to dial down during your workout or you might start out feeling bad and things turn round after a 15min easy walk.
Coming up with a daily number that is not representative will do more harm then good.
Once you tailored your training plan to your individual physiology, things should go smooth most of the time. And you will know that something is wrong when you run into difficulties. Are you getting sick, having a temporary stress situation, gastro-intestinal problem, etc…
Agree with @MedTechCD . As someone who has been coaching hundreds of athletes for 10 years, any Training Readiness number (be it from an app or wearable such as Oura or Whoop) does not necessarily correspond with performance on the day. If you use a wearable such as the Oura ring, you can connect it with Intervals and have your scores from it (including readiness, HRV, etc) show at the top of each calendar day. That would give you a nice visual to compare to the performance metrics of a given workout on that day.
But even then, I always recommend that athletes only look at their scores retroactively, as it doesn’t commonly align with performance.
Zwift added this feature on their main page in Companion App and here again, it rarely aligns with reality.
We use a multi-factor formula to track fatigue and readiness to perform / freshness / whatever you want to call it - pretty much as @MedTechCD says - there are a lot of moving parts to track.
The formula includes tracking external load (work done) - power numbers for example - and internal load (the body’s response to that work) - HR, RPE, simple subjective wellness questions - these are all bundled into a fortnightly submaximal fatigue test.
We have covered monitoring training load quite thoroughly in our latest posts on sciencetosport.com -
Submaximal Fatigue Test for Cyclists & Coaches - How to do it
AlphaHRV also provides readiness score after 10 minutes starting an activity. You can enable/disable notification on the watch, as it can be de-motivating if this is not in line with how you feel on that day 
I’m using it as described above more post analysis after the work out and keeping an eye on it during the training plan. I also look at my HRV stats from Garmin, however it’s not perfect and sometimes I have a different perception. Sleep quality is also key. Many indicators, so I understand the challenge to display everything on Intervals as metric to detect trends, I have the same challenge
The wildcard for me in training readiness continues to be strength training. I know there are threads elsewhere in this forum that discuss calculating strength training load, but I find that those still don’t translate well at least in my case.
I think the issue is strength is neuromuscular load and riding a bike is mostly endurance / cardiovascular load (workout dependent of course - racing, sprints and torque intervals include neuromuscular load). Two different systems.
The issue is they don’t compound in a linear fashion when combined. Everybody has a different response to training each system, depending on things like genetics, training history and current fitness for each type of load.
You can use internal load monitoring to better track the combined load. Subjective wellness questions, RPE, HRV and so on.
I am using the BPE method with Z-score, taking into account several parameters, and it is very close to reality. Then, at the HRV level, I also use a combination of lnrMSSD together with a z-score, which also gives very good results because it highly customises the values.
Yep, hence my comment. HRV can and often has a bit of a delayed response. I’ll continue resorting to Respiratory Rate, fatigue/soreness, mood/motivation (which captures the neurological aspects of fatigue).
I can imagine how this would closely align, just not willing to go through the work