thanks. I dive with a standard watch as a timing device. I guess I didn't think the VT3 would naturally replace that so you make a good point. I think I'll try it on my right side this weekend and see how it goes. If I don't use it or it seems awkward I may just leave it in my dive bag and only grab it (and a watch) in case of an emergency.
Let me give you my opinion as to why as a REC diver having a backup SPG hooked to the regulator is not essential. As a recreational diver who uses a dive computer (BTW, I use the Aeris Elite T3 which is the same as yours except for the name), if the thing were to give you some weird, crazy readings, it's pretty simple. You terminate the dive and surface.
In this scenario, an SPG gauge does you no good other than adding more drag and weight. It doesn't matter how much air you have left in your tank, you go up anyway because of major equipment failure. It's no different than if you were to use an SPG and it fails on you. If your analog depth gauge were to fail on you, same thing - terminate dive. And naturally, you don't need a depth gauge to tell you that you're getting close to the surface since that you can see it coming as you rise up.
If you have enough air to do a safety stop, then do a safety stop and look at the surface to judge the distance.
Here's why I am going to explain why having a backup/separate timing device is a lot better than an extra hooked up SPG console. As you dive more often, you should know your approximate SAC (varies slightly depending on how hard you swim against the current, distance you've swam, depth, etc. but more or less can be averaged out) and approximately how long a tank of certain capacity would last you underwater.
Let's take a look of my own case. I dive with an HP100 tank and at depth of around 60-80ft, it will last me to around 40-minutes (I'm an air hog) with plenty of air for safety stop and easily 500-psi leftover at the surface for emergency. So, if my computer were to conk out, I'd simply look at my watch and see how long I've been underwater. 20-minutes? 30-minutes? No problem, I have plenty of air for safety stop. Ascend, do safety stop, then surface. Do a square profile dive calculation based on the max known depth (I should know this from the boat captain/dive master's briefing ). Whip out the spare SPG console, hook it up and keep on diving.
If I had dived for 40-minutes or so according to my watch, then I may do a shorter safety stop or simply surface.
If I were to dive at around 30-ft then I'd know that my tank would last me 60-minutes plus reserve and I'd do the same thing as mentioned above. If I were to dive at 80-ft or deeper, I'm going up in a controlled fashion, but I'm going up and surface.
So, for me as a rec diver, I see no use for an attached SPG console.
Of course, another option is to buy an extra dive computer and hook it to your BC or wear it on your wrist as a backup. But then we're having backup for backup for backup for backup. Where does it end? YMMV.