I thought of this today and was about to post a topic and I saw yours.
Yes, I also think this is much needed feature, as exposing the DSM interface to the internet is risky.
I understand that it probably would be only Android/iOS application, as sending text messages is an additional cost, however my guess is it is completely doable to implement such feature. Such security measure is extremely important since the data kept on Synology products is usually important and private.
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