Phone and headtorch only.
I have experimented with a solar battery pack recharger. However, its a significant additional weight and isn't that reliable in typical UK weather. To work well it needs to be setup facing the sun and left for a good few hours - just carrying it strapped to my rucksack and hoping it was in the sun enough was relatively ineffective. And its still necessary to carry a battery pack to store the charge from it.
In practice, even on a long walk, I think I'm better off just with a small battery pack (say, 5000mAh) than a solar recharger. With my phone on aeroplane and battery saver mode it will last about three days, even with intermittent use for mapping and photos, and a battery pack will more than double this. Hence I'll be needing to make contact with civilisation (and hence recharging opportunities) due to running out of food before I'll be running out of power.