Seedless blueberry jam - consistency I was trying to customise blueberry jam for a friend who did not like the jam with the entire fruit in it. So I had to filter out the seeds and skin. But the consistency is always a bit runny. 

I use Frozen blueberry and for 650 grams of blueberry I used 150 grams honey. 1/2 a lemon's juice. 
Thawed berries and heated a bit, filtered the pulp and juice. Then added the honey and lemon juice . Brought it to 96°C (205°F because if I boiled more than 98°C it became too hard) and cooled down before packing.
Blueberries are generally low-pectin fruits, so many jam recipes and jam making guides specifically call for adding pectin. That said, some do not - but these use the whole pureed fruit. When you filter out the seeds and skin, you remove much of what pectin there is in blueberries naturally, leaving you with runny jam.

The solution, then, is to add pectin or some other fruit that contains some.

As a note, unripe fruit, including blueberries, often has more pectin than ripe, but if you're using frozen blueberries, they're likely to be picked at their peak and rather low in pectin.