Usually, what gives jam its "jammy" consistency is a mixture of sugar and pectin, or sugar and lemon juice. But given that fruit already has a lot of natural sugar, pouring another bag in isn't always ideal - especially now that we have an alternative readily available.
Chia seeds are a great way to give jam a nice texture, while adding a good pop of omega-3s and letting the flavours of the fruit really shine. You can grind them up, or leave them whole if you like the texture (eg, we're already accustomed to having seeds in our strawberry jam). Just mix them into your stewed fruit, and leave it to set the same way you would a chia pudding.