This item shares exactly the same properties as the Sign of Life, except it requires the highest divination level to create, and its not a pocket slot item, and therefore it stays in your inventory.
The Sign of Life on requires level 78 Divination, is tradeable (making the Divination level not necessary), and on top of that, you can equip it, freeing an inventory slot.
The Portent of Life requires level 99 Divination, is NOT tradeable, and you cannot equip it. The only advantage I see in making this is so you can equip a scrimshaw at the same time of being able to use this.
Do you see what I mean?
Though being able to wear a scrimshaw at the same time as using this is handy, I still think that maybe making the Sign of Life NOT tradeable would make people more likely to actually get that level, and also possibly making the requirement for Portents of Life lower.
Another way to maybe make the Portent of Life more desirable would be to make the Sign and Portent of life not share the same cooldown. To counteract that, you can’t have both in your inventory at the same time/be wearing the Sign and withdraw the Portent from your bank/GE/trade with another player.
This way, you can use one of each within the hour (so two), which would make the Portent more desirable.
This is just my thought on these Divination Runescape items, and how I think they could be better.