Jean-Luc F6HOY added an analog s meter to his first BITx40 with a simple circuit on an audio line and a 500 microA vu-meter. All was fine except that without any AGC it only provided an indication of the signal level.
Jean-Luc added a Chinese Audio Vu-meter that is much better on his µBITx.
For around 15€ he received a circuit module and 2 vu-meters. Only one vu-meter is used of course. The circuit board functions as an AGC, and for an extra bit of fun he has a nice warm light in the shack from the yellow light of the VU meter.
You can get this kit from several shops in China (one such example).