It was previously available on the iPad -- also, everything else
Previously, Machinarium was only available on the iPad branch of the iDevice family, but as of this week you can grab it on your iPhone by way of Machinarium Pocket Edition. The App itself has become Universal, so if you own it already on a previous device, just check your history and re-download it.
The new Pocket Edition arrives with Retina support, achievements, zooming features, and iCloud support, and is priced at $1.99.
Machinarium Pocket Edition [iTunes]