It is ad hominem because you implicate anyone who worries about one device to stop worrying because you can choose from a bouquet, some other flower they should be more worried about.
Gun safety says it's unwise to point a gun, even an unloaded or uncocked gun, at someone you don't wish to shoot. In the same vein, it's unsettling to have microphones and cameras around one's house _even_ if you suppose they are off. Because the latent ability is potential oppression.
Ad hominem is quite explicitly attacking the person who made the argument, and not the argument itself.
I believe the fallacy you're looking for is 'fallacy of relative privation', but even then, we're still not there. Fundamentally, the issue is this:
The fear is that the microphone could be used as a listening device. From the current factual information we have available, we know, at this time, that:
1) Law enforcement agencies can and do use cell phones as listening devices, both in intercepting calls and remotely enabling the microphone.
2) It is not possible to see all traffic that is flowing through your cell phone in many cases (iPhones, non-rooted Android phones, etc)
3) It is possible to see all traffic that is flowing through your home network. If it is encrypted you might not be able to determine the specific contents, but you still have the technical possibility to see when communication occurs
4) We do not currently see any evidence that the Echo performs any sort of recording or transmission of voice data outside of when the 'wake word' is used.
You'll notice nowhere did I say these fears were completely unfounded - just that there is no evidence to suggest this is occurring, and that if it were occurring, we would not be without ability to detect it. But by the same token, these selfsame fears, that an electronic device can be used to listen in on you, are 100% confirmed to be true with cellphones. We know that they can be used to listen in on you. Therefore, if your concerns are your electronics being used as a surveillance device, then cellphones are a clear and present risk and should not be owned.
And if we're throwing around fallacy accusations, and your argument is "We shouldn't have remotely accessible microphones and cameras around, because they'll be used as surveillance devices", then you're participating with a classic slippery slope fallacy - but I don't think all of the fallacy talk is particularly productive, either.
Gun safety says it's unwise to point a gun, even an unloaded or uncocked gun, at someone you don't wish to shoot. In the same vein, it's unsettling to have microphones and cameras around one's house _even_ if you suppose they are off. Because the latent ability is potential oppression.