Carnivorous Flower-worm: Implantation Possible?

Question

If you want to know exactly what creature I'm referring to, look at Feasibility of Carnivorous Flower-worm. Let's say I want people to be able to ritualistically implant these creatures to gain the benefits of increased energy (from their photosynthesis) and a monster alarm system (from their creature-sensing ability).

This requires a few abilities:

1. Ability to connect to nervous system/release chemical signals into the host for communication

2. Be able to share nutrients with the host

3. Be able to extend "roots" that it can regenerate from if it's cut off

4. Be able to sense and differentiate from organisms around it

How can this be made possible?

Please Note: I'm not asking you to explain how this creature can be implanted into a human being, but rather I'm asking you to explain how the four abilities above could work. In other words, I'm asking for adaptations that would allow it to function as an implant, not an explanation of how it could be implanted.

As for why: As an interesting feature I pictured a race of extremely nature-attuned people (Forestkin, they see themselves as an extension of the forest, one with nature) cutting themselves and then implanting an Anklebiter (AKA flower-worm) in their wounds. The Anklebiter would allow the Forestkin to gain energy from the sun and sense nearby living things, making hunting and evading monsters much easier. I picture these Anklebiters being implanted behind the ears, as these worms do look like flowers after implanting.

What, Exactly, Am I Asking?

1. I'm asking for explanations for the abilities above. Magic is involved, but not much, so all I really need is a biological basis for each ability.

Answer 1

All of those traits already exist

Each one of the listed traits exists already in some format, though not quite all together

Releasing chemicals to communicate

Many animals (such as the octopus) are known for spraying out various chemicals for defense and attack. While few of these sprays are for communication, it's not hard to imagine that the right excretion in the place could interface with the nerves

Sharing Nutrients

Mycorrhizae are a common type of symbiosis involving a plant and a fungus exchanging nutrients. However, similar systems can exist in many species, and so it isn't implausible that this flower worm could have its own symbionts. And it's not so implausible that these symbionts, already adapted to animal symbiosis, could complete the connection between the host and worm

Extending Regenerating Roots

Sacculina are a species of parasites that, instead of a simple mouth and gut, extend their head into a system of roots that penetrate their host. While I don't know if Sacculina specifically can regenerate, it's not implausible that the structure could have regenerative power, especially in a carnivorous species like your flower worm

Sensing thing in the surroundings

This trait is something found in almost every animal, and seems like it'd nearly be a requirement for a carnivore. There are also many methods that fit into their mimicry, such as vibration-sensitive hairs on the body, using the petals as olfactory sensors, or a set of eyes disguised as buds or berries

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These traits could easily be found together in a single creature

Chemical release is a rather common adaptation across many clades, and there's no reason to assume the flower-worm couldn't join in

Mycorrhizae would be rather useful if it photosynthesized, and wouldn't be that hard to adapt for

Sacculinoid roots might be a little harder to justify, but there are still explanations; Perhaps they could be faculative parasites able to live in live animals as well as the ground, which would also bolster their abilities to survive the implantation

Senses are a universally common trait amongst animals, to the point where it'd be harder to justify if they didn't have them