Headphones

In a word no. The Sonos app is just a controller. There used to be a headphone socket on the Gen 1 Play 5 so you could pick up one of them. I don't see the need though. Surely you have a phone or PC that you can play music to headphones from?

Sure I have a phone (or iPad) that I can use, but it would be nice to listen to some of the playlists I have made for "my Sonos" -- using my phone.

I see. Yes, it's annoying that there is no way to export and save playlists 😞

Not through phone but an option for headphone use in-house is to connect the line out of a Sonos Connect to the base station of a wireless headphone.

You could get a sonos connect and fit a Bluetooth adaptor to its output, and use wireless Bluetooth headphones.

Paulw123 -- thanks, but I have a really good set of Bose headphones (corded), and I would like to find a way to use them either with my phone or iPad.

oh I see.
Maybe a connect with phono male plugs lead to 3,5mm female lead.
https://www.amazon.co.uk/Ollivan-Universal-Stereo-Female-Adapter-Black/dp/B015446ZMI/ref=sr_1_13?ie=UTF8&qid=1528967914&sr=8-13&keywords=phono+to+3.5mm

A gen 1 Play 5 has a headphone output and ebay has a lot of them listed.

With the Connect, the RCA outputs will drive most headphones with an RCA to 3.5 adapter.

You can also hang a Bluetooth transmitter off of either Sonos but the music in your BT phones will be out of sync with your speakers.

To be more clear --- I'm trying to find a way to use my headphones through the Sonos app, but without using any of the Sonos speakers. Think listening to the music within Sonos without waking the baby.

As was said, you can't do that. The controller is just a controller, it reads data from your sonos devices and sends them commands, it does not read the music data, just the tags.

If you use one of the streaming services you can stream that to your phone or tablet. You can also stream your music library, maybe using Plex?