Our 2003 Jazz came with the original stereo / CD player, which always looked like it would be a big problem to update with anything more modern given the very curved and specific mounting of the unit in the dash.
A couple of years ago, I took it out to repair the common voltage regulator fault, and while it was out, I fitted a small, dedicated Bluetooth circuit board to the AUX input and as this neatly fits inside the stereo space, there are no trailing wires to get everywhere, and that neatly ticked the Bluetooth box at very little cost.
To give ourselves a sat nav option, I bought a magnetic phone holder which firmly sticks to one of the few flat areas on the dash and now gives us a tidy place to attach the phone, and it really does work and almost looks "factory fitted".
I know that everyone has their own satnav favourites, but two of my favourites are the ones that use the Open Street Maps to work. Osmand is probably my favourite, but Organic Maps is well worth a look as you can download maps for the entire world to it freely.
It was created by one of the originators of Maps.Me and is lightweight, absolutely no ads, totally free and works completely offline.
I'm currently trying to work out how to mount a Samsung Galaxy Tab Active 2 securely in place, and am considering a CD drive slot mounting attachments, but we don't really need it, to be honest as the phones work really well on the holder.