Basic idea of a redstone-activated block in 0.13 (definitely works). Won't compile as-is, obviously.

Redstone Block.cpp

// however you're adding blocks
initBlocks hook {

    // create & register a MyBlock instance etc

}

CircuitSystem.h

#pragma once

#include <memory>

class BlockSource;
struct BlockPos;
class LevelChunk;
class BaseCircuitComponent;
class ConsumerComponent;
class PoweredBlockComponent;
class ProducerComponent;
class BaseRailTransporter;

#include "../../../CommonTypes.h"

class CircuitSystem {

public:
	char filler[88];

	CircuitSystem();

	void cacheValues();
	void checkForAssociatedNewPoweredBlocks(BlockSource&, BlockPos const&);

	template <class ComponentT> ComponentT* create(BlockPos const&, BlockSource*, signed char);

	void createComponent(BlockPos const&, signed char, std::unique_ptr<BaseCircuitComponent>);
	void evaluate(BlockSource*);
	void evaluateComponents(BlockSource*, bool);
	char getDirection(BlockPos const&);
	unsigned char getStrength(BlockPos const&);
	bool hasDirectPower(BlockPos const&);
	bool hasNeighborComponent(BlockPos const&, int);
	bool isAvailableAt(BlockPos const&);
	void lockGraph(bool);
	void onChunkDiscarded(LevelChunk&);
	void refresh(BlockSource*);
	void removeComponents(BlockPos const&);
	void updateDependencies();
	void updateLevelChunk(LevelChunk&);
	bool validPowerBlock(FullBlock const&, FullBlock const&, BlockPos const&);

};

MyBlock.cpp

#include "MyBlock.h"

// necessary includes eg. Level, BlockSource, BlockPos etc
#include "minecraftpe/world/level/circuit/CircuitSystem.h"

void FloodgateBlock::onRedstoneUpdate(BlockSource& source, const BlockPos& pos, int strength, bool b) {
	// react to change in redstone here
	// eg.
	if(strength) {
		source.removeBlock(pos); // remove this block (set to air)
	// source.getLevel()->explode ???
	// do something else cool
	}
	// or do anything else really
}

void FloodgateBlock::onPlace(BlockSource& source, const BlockPos& pos) {
	Block::onPlace(source, pos);
	// also call code to add the circuit component
	// needs to be done on world load & on block placement
	this->onLoaded(source, pos);
}

void FloodgateBlock::onLoaded(BlockSource& source, const BlockPos& pos) {
	// only perform server-side
	if(source.getLevel()->isClientSide()) return;
	// add component to circuit system
	CircuitSystem *system = source.getDimension()->getCircuitSystem();
	system->create<ConsumerComponent>(pos, &source, 0);
}

MyBlock.h

#pragma once

#include "minecraftpe/world/level/block/Block.h"

class MyBlock : public Block {

public:
	/* add constructors, other methods etc here */
  
	virtual void onRedstoneUpdate(BlockSource&, const BlockPos&, int, bool);
	virtual void onPlace(BlockSource&, const BlockPos&);
	virtual void onLoaded(BlockSource&, const BlockPos&);

}