I am a software engineer / programmer.
My 2 cents are that even 50% is an absolute rip off for any programmer worth their salt. If someone wanted to partner with me where I did all of the work and they just had some idea they thought up in 5 minutes, I would expect a vast majority of the lions share (99.9%).
Ideas are a dime a dozen. No really. They are. You are not special. Do you think that out of the ~7 billion people in the world with hundreds of millions much much smarter than you - that you have developed an original idea? Success is largely measured not so much by the idea, but by the execution. Look at Google. They were very late in coming to the Search Engine game. Yahoo, Alta Vista, Excite, etc... had been around for years. Their execution? Amazing.
1) Hire / contract a developer to build it, that way you can retain ownership and receive all of the profits.
2) Partner with a developer. But if they are doing most of the work - they get most of the pay. If it took you say 10 hours to develop the idea and provide a spec / design for the developer and it took then 90 hours to implement it - then in my opinion: The developer should get 90% ownership, and you 10% ownership.
Basically: Actual hard work / time is rewarded. Anything else is absurd.
Don't forget to take into account maintenance and support of the product past the development state. This is real "work" and should be compensated appropriately.
Now if you are going to be doing other real work, like forming the LLC, managing all the finances, contracts, invoices, legal, taxes, customer support, etc... then you can up your share. Why? Because you are then contributing more "work" and time.