Minecraft – way to automate harvesting cobblestone

Both Technic Pack and Tekkit include ComputerCraft, which gives you access to Turtles, one of the most wonderful automation tools.

A Turtle is a programmable block just like a computer, but it has an inventory and is capable of movement, digging (when upgraded to be a Mining Turtle), block placing, and sensing its environment and inspecting the contents of its inventory. You might already be familiar with the Mining Turtle's use with macro commands – excavate and tunnel being popular – but since it's a full-fledged a CC computer block you can program it with Lua directly. Giving it a program with a combination of looping, movement, and block placement commands, you can have a Turtle build arbitrarily complex structures.

If you're really ambitious, you could build Wireless Turtles and coordinate them via Rednet from a single program running on a central computer.

(As with most automation, Turtles don't like being unloaded as part of a distant chunk. The usual solution of World Anchors or Teleport Tethers can be useful for long-running construction programs.)

Wondering why your Quantum Helmet doesn't operate as advertised? As of IC2 v1.110, the Quantum Helmet can refill your hunger with carried canned food, at an EU cost of 10,000 EU per point. And, of course, at the cost of carrying said canned goods around.

Alternatively, you could look into foods with higher saturation. Ambrosia, crafted from bee products, gives high saturation (and 40 seconds of regeneration). Or, if you don't want to bother with that, steak is always a good option.