If you like to do things yourself around the home, then maybe a cross- & line laser could be useful. The voltage on this tool is 2 volts.
From ManoMano
Stabila - 19794 LAX600G Green Beam Multi-Line Laser 12V Bare Unit STBLAX600GK5
Conrad Electronic
Stabila LAX 600 G, 12-V-System, 5-pcs Multi-line laser Self-levelling Range (max.): 40 m