African Clawed Frog eggs are actually frequently used in laboratory settings for their exemplary ability to express olfactory receptors. Basically, the eggs, still immature, were injected with DNA from insects like fruit flies and silk moths, which stimulate the eggs to start producing olfactory sensors. The eggs are unusually able to detect pheromones and other gases.
The genetically modified eggs were placed between a pair of electrodes to form a detector, which measures the current created when the receptors on the egg bind with the odor molecules. The frog egg detectors are far more sensitive and accurate than other biological smell receptors that use the physical vibrations of quartz rods that vibrate when target odor molecules bind to them. These detectors tend to give false positives when other molecules with similar molecular weights to the target molecules bind to them.
The new frog egg smell sensors were embedded in a robotic mannequin that is designed to shake its head whenever it has a positive response to a scent. The sensor is extremely precise, able to detect moth pheromones with a very high degree of accuracy, especially when compared with other biological smell receptors.
While it may sound goofy, the frog egg smell sensors actually have a wide range of possible application, from bomb sniffing (literally! Ha!) to biomedical replacement to food allergen detectors.