If a web-app is acceptable
MerriamWebster will do fairly well on that. One caveat; if it is already a real word but not the word you want it won't give suggestions. It is free, however there is no offline or self-hosted option. They do have iOS and Android app versions but I haven't used them so don't know for certain whether they have the similar word feature.
An example would be say I was meaning to lookup hmm eldritch and input instead eldrach (a instead of i, deleted t) it would suggest: