A healing pod is a structure found In Frieza's Ship. It is not an Item, Or and Entity unto it self, It's made of multiple parts.
Silver Colored Stone Blocks
Silver Colored Stone Blocks, are the blocks that Frieza's ship is made out of make up the body of the healing pod. They serve no function besides shaping the pod and keeping the water in.
Medical pod door
The Medical Pod door, is a special block that when left clicked opens like a sliding door, with half the block going in either direction. Also even when open it keeps water inside.
Medical Liquid is a special kind of Minecraft liquid. It displaces like Normal water, but if submerged, it will occasionally refill your oxygen meter and refill your health.
Medical pod door
A Medical Pod door is, A door, but unlike normal Minecraft doors, which move 90 degrees. if you left click one it will break in half, and each half will move into the blocks adjacent to them, without breaking the block their moving into. left click again in the space were the door was will make the two halves come back together, closing the door
Effects on liquid
if the is liquid behind a Medical pod door, it will not flow through when it is open, making sense for keeping in healing liquid.(then again, so does any other Minecraft door so...)
When a medical door is left clicked to open, it will also open any medical door directly beneath, or above it. This means that the most medical doors you can open with one button press is 3, as it won't open every medical door in a vertical stack.
Medical Liquids Physical Properties match Minecraft waters. If not contained on all sides by other blocks, besides above, it will flow, and if you are submerged in it you will start to drown. Medical Liquids operate the same as water, it can turn into cobblestone and turn lava into obsidian.
However Medical liquid has some special properties, if your submerged in it, it will heal you, and intermittently replenish your oxygen meter.
These Properties work without the presences of Medical Pod Doors, or Silver Colored Stone Blocks. Thusly you could make a healing pod out of anything, if you could craft or move the Medical Liquid.
There are special herbs called "Healing Moss" in planet Namek, they look like bushes that drop seeds, but they drop medical moss items instead. At the very top of the list you can exactly see how to craft a bucket of medical liquid here:
Just create yourself some kind of a pool and pour that in there, it will keep healing you as long as you are inside. You can also collect medical moss from Namek, return to Earth, and you can plant them on trimmed dirt, so you will have your own medical moss farm.