I have acquired an iPhone 3GS in order to be able to occasionally tether with my iPad mini (wi-fi). The Apple website said I could do this over Bluetooth. I tried it on a train a few days after getting the phone and it worked very well, just as fast as when I have used other phones with wi-fi tethering.
But then the next time I tried it wouldn't even connect/pair with the iPad and it hasn't done since, the iPad can't even detect it. I did once completely restore the phone and I noticed that it did detect the iPad for about 3 or 4 seconds then it lost it.
The iPhone has IOS 6.1.3 and the iPad Mini has IOS 7
Any thoughts?

Thanks to those who have looked.
I have now worked out that the two devices aren't really compatible. They can pair…………. but only just! It seems that the iPhone 3GS is just too old to work properly with the new iPad Mini. I have found a way to get them paired but it's very hit and miss and can't be relied on.

It's a shame that Apple's designs don't allow for this downward compatibility. The phone is perfectly good but I am now forced to replace it. I think that Apple are starting to behave like a company that make people buy the newest and the latest, and will restrict their products to force this.

What do you think?

What you're asking for could be called "perpetual backward compatibility". Apple has done a good job of maintaining this, but not forever. There are significant hardware changes/improvements in the new iDevices, and at some point the "old" (which may only be 3 or 4 years old) have to be let go.

A very nice use of your iPhone is to turn it into a remote viewing camera, for free. Check out Presence . I use it and it is rather amazing in its free capabilities.

Bluetooth is usually pretty good about backward compatibility. There's nothing special about Bluetooth tethering that should make a modern device unable to tether to an older iPhone; in fact, my 2012 Macbook Pro tethers with my old iPhone 3G.

However, having said that, Bluetooth tethering is a finicky beast. I have an iPhone 5, and my computers will successfully tether with it about 2 times out of every 3 that I try. Other times, I get cryptic error messages, requests to re-pair the devices, or it seems to link but I get no network.

For that reason, I usually prefer to tether by setting up a Wifi hotspot on the phone and linking via Wifi. This seems to be a lot more reliable.

I have to say that I think you both have a point. As far as Apple's support for the 3GS goes, that's still there, in full. We're not talking about 'vintage' let alone 'obsolete' hardware. That said, interactivity with newer hardware is not guaranteed, as is other functionality developed or improved after the 3GS manufacture/specs finalization. As to the specific tethering issue you're dealing with, I can't tell if that's subpar or to be expected. A visit to an Apple Store might be enlightening.

I see Ira's point too, but I'm afraid that only goes so far. Despite what I said above about certain functionality not being guaranteed, I don't see how 4 years (approx. age of the 3GS) equals 'perpetual'. And if—for all practical purposes—it effectively is, I predict that the associated apparent speed of 'obsoleting' hardware will run into some user backlash sooner rather than later. Not that that helps you, how much fun Presence may be.

> ...I predict that the associated apparent speed of 'obsoleting' hardware will run into some user backlash sooner rather than later.

Although it's not precisely on target, the 25-30% of Mac users who have refused to upgrade past Snowy may be considered the first instance of backlash.

I'm one but I'm about to buckle. Too much new software won't run on 10.6

I've been lucky so far, because none of my apps that now require 10.7 or higher has offered any new functionality that I've either needed or wanted badly enough to induce me to take the plunge; you're more vulnerable than I am, but I suspect that a significant portion of Apple's user base is in my position.

I've been pointing the Snowy backlash out to the devs to whom I speak in the most likely vain hope of inducing them to maintain backwards compatibility (A consistent problem has been that they've upgraded their own OSes and no longer have Snowy machines for testing.), but it's really up to Apple at this point; their approach to dealing with the the backlash (I suspect that reinstating Rosetta would go a long way for them.) will most certainly govern.

I bought my new deuced Mac(hina) in the hope of buying a lot of years along with it, and I've got my fingers crossed; after all, there are still users running OS 9.

Footnote: I've got a Lion Thumb Drive Installer socked away against the day Intuit abandons 10.6.8, as the've recently abandoned 10.5.8, but I'll maintain a separate partition for the exclusive purpose of running TurboTax, hopefully for as long as my current machine will run.

That's me. The investment in new software is huge....especially when the existing software is doing everything I need it to do.

I gave 10.7 a miss when it came out, as I think 10.6 is one of the best OS versions Apple has ever released. I grudgingly installed 10.8 on an external hard drive recently simply because I have to test software under it, then decided I liked it enough to install it as my main OS.

I started using 10.9 Developer Preview 2, also to test software, and I have to say Mavericks is the next Snowy. It's awesome. They got a lot of stuff right. I suspect 10.9 is going to stick around for a long time.