Oracles, Statues and Idols

The Precursors communicate (presumably from the planet's core) to elves, be it Jak or monks like Seem, through various oracles, statues, and idols. Doing so requires two devices: a transmitter and a receiver akin to the way radios send and capture radio waves. Whether this is radio, or some kind of eco energy, can only be hypothesized.

Transmitters

For most of the games, the Precursors are seen as long gone race that mysteriously disappeared eons ago. So it's not evident that the communications through oracles is anything other than strange magic, or just a pre-recorded, generic message. At the reveal of the Ottsel Trio at the center of the planet, a hand held device is seen held by the ottsel leader, in which he is speaking into it, and his voice is changed to the familiar, deep and cryptic voice affiliated with the Precursor artifacts.

See the transmitter in the middle ottsel's right hand

It's only seen in this scene, so its functionality can't be easily ascertained, however it closely resembles a microphone with a pop screen, and utilizes some kind of voice changer.

Receivers

Various receivers are seen through out the world, in a much higher number than transmitters, most Precursor in origin, but some may have also been made by the Wasteland's Precursor Monks, who, according to Seem, have direct communication with the Precursors.

Oracles

The oracle found in Haven City

Precursor Oracles are found all over the world, sometimes holding powercells, but these are not necessary to their power, as ones without them operate just fine, and Jak is given these powercells in exchange for orbs¹ all through out his pursuit of Gol and Maia.

The powercell leaves the eye, down the snout and out the mouth for Jak to pick up

They usually offer cryptic advice, all with the same deep voice later seen coming from the handheld transmitter. Once possessing dark eco powers, Jak is given certain abilities from the oracle in Haven as well, in exchange for metal head gems.

The precise reason why the oracles look the way they do is never specified, but the snout is common in both these, and the Precursor Robots.

However, once in the wasteland, these types of oracles are instead replaced with statues with a much different aesthetic and size.

Statues

Considering how similar they look to the huge idols found in the Monk Temple, it may be fair to say that these were created by the Monks themselves, as ways to communicate with the Precursors. They also look very similar to the statues found in South Haven Forest that unlock the The Astro-Viewer².

Idols

The huge idol found deep within the Monks' Temple has three different faces³, and as Jak visits each one, he is given a light eco ability to counteract the dark eco. This is also where he is transformed into Light Jak for the first time.

The idol is where it's first shown that the voice coming from the Precursor Oracles may not be just some pre-recorded, impersonal sign, but a real-time communication device, as Daxter chides the statue and receives an insult in response ("I was talking to the tall one, shorty.").

Seem also learns sooner than Daxter, the true nature of Daxter's change in the dark eco vat, going from being annoyed, to revering him. Already knowing that Daxter was "the color of our creators", which in itself indicates communication between the monks and the Precursors of some kind, to saying they were glad to see the faces of their creators before the world ends, and petting Daxter. This new information shows real-time communication as well⁴.

Headcanons and Notes

1. What Precursor Oracles needed the orbs for is never said, if they are needed at all and not just a trial for Jak to train through. Same with the metal head gems in later games.
2. Did the monks lock away the astro-viewer? If so, why? This might also explain why the artifacts needed to power it are found in the wasteland.
3. Does this line up with the three precursors at the core of the planet? Does each one give Jak a light eco ability?
4. Do the idols know that Count Veger was planning on going into the catacombs, hearing him speak to Seem about it?