Blutz Wave Amplifier
From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
The Blutz Wave Amplifier was a machine that amplified natural Blutz Waves by 1000%. It was built by Bulma while she was under Baby's control. Saiyans may transform into Great Apes even without a tail if the energy given by Blutz Waves is correctly amplified, and therefore this machine may be used on tail-less Saiyans.
It appears that an artifically high concentration of Blutz Waves can also be used to re-energize a Great Ape. Using the Amplifier, Bulma was also able to bring Great Ape Baby back to full power after he been knocked out by Goku.