Hi Stuartv, thank you for responding to my additional questions regarding your diving and how you use your computers. The questions you have to Scubapro/Uwatec are valid and these are the same questions I have pondered over.
Let me take this opportunity to share my experience with heart rate training. First, to take advantage of this technology it is imperative that you work out your maximum heart rate (MHR). The formula of 220 minus age is too general. And your running MHR is not applicable to diving because water is supporting your body while diving. The MHR for diving or swimming is lower for the same amount of effort; about 10 to 15 beats per minute. The MHR has to be accurately determined because the trigger to change the decompression profile is going to be based on a percentage of MHR (or your heart rate reserve (HRR) which is the difference between your MHR and your resting heart rate). I suspect the trigger is around 85-90%. I wouldn't be surprised if many divers using the Galileos and G2 have left the heart rate settings at the default of 100/180 and the trigger never kicks in because the 180 is too high for a swimming/diving MHR.
When I go for my run, and I push my effort (workload) to 90% of my MHR - guess what happens to my respiration. It naturally increases because my body is demanding more oxygen. On land, I don't need a transmitter screwed into my neck like Frankenstein to monitor my breathing rate; respiration can be derived from my heart rate. The training software I use can graph my heart rate and my breathing rate; all from my heart rate monitor.
When you plan your dive, you are making assumptions about your average respiration. As long as you are calm and breathing normally, you complete your dive as planned. But say something happens at depth to increase your workload to 85-90% of MHR. You have 3 problems. First, you have to fix whatever it is to reduce your workload. Second, you consumed more gas than planned (increase workload naturally increases respiration) Third, because you inhaled more oxygen; you absorbed more nitrogen at depth. You muscles demand more O2 which your heart delivers, but O2's buddy is N2 who came along for the ride and doesn't necessarily want to leave!
So what do you do? Your plan is blown; it no longer applies. You have less gas than planned and you have more nitrogen in your system than planned. You go through your decompression profile and at 6 meters, hopefully the boat skipper has dropped two hookah lines for you and your buddy which is connected to a tank containing 100% O2 on the boat. And you suck that gas like an infant on his mother's breast until you get the all clear to surface; either by sucking the tank dry or by your dive computer which took into account the diving incident.
The idea behind the heart rate monitor is to objectively identify and measure an increase in workload so that it can be taken into account for your decompression. Your Shearwood kind of does the same thing but it measurement is subjective. On page 59 of the Perdix manual;
"The conservatism settings (GF High and GF Low) can be edited in the Dive Setup menu. While diving, only the GH High value can be edited. This allows changing the surfacing conservatism during a dive. For example, if you worked much harder on the bottom segment than expected, you may wish to add conservatism by reducing the GF High setting."
In my OP I asked Shearwood users what's in store for the future; what will they create so to make their Terics obsolete. Shearwood may incorporate heart rate monitoring but use a different approach to Scupapro/Uwatec. The additional deco obligation may be calculated in the background and a warning message pops up saying; Workload Increase. Suggest change GFhi 85 to 75. Then it leaves it up to the diver to decide if he wants to make the switch or not. This approach may be more acceptable to divers because it leaves them in control of their decompression profile.
