It depends on what feature of Pocket you are asking about.
If you are asking about features that operate primarily on your desktop or laptop computer such as the addon that works within your browser then it could well be on topic here.
If you are asking about the website or web application then Web Applications would be a better place for it.
For integration with or applications on other platforms then it would be better on those platforms Stack site as mobile phones and "random electronics" are off topic here.
- https://android.stackexchange.com/
- https://apple.stackexchange.com/
- https://windowsphone.stackexchange.com/
If it is about how the backend works and how posts are transferred between platforms then it is probably too broad, too programming focused and cannot be guessed by "normal" users then it may not have a place on the network. You might be better off contacting the developers directly.
Without more concrete information on what questions you are going to ask all I can say is that each question would have to be taken on a case-by-case basis. You should really read the /help/on-topic page for each site (i.e. https://superuser.com/help/on-topic, https://webapps.stackexchange.com/help/on-topic) to find out what is on or off topic for each site.