We do not have any at home but y wife works for an establishment (& I am a volunteer there too) where there are keyless codelocks on virtually every door, internal and external.
Though this is an English site, it shows the flavour of what is available -
Electric and Mechanical
One tip if you fit one: change the code fairly regularly. If left on one code, over a period of time, those buttons start to show wear and reveal the 'active' ones..On a 4 digit code that makes 16 combinations to try!