PROMISSORY ESTOPPEL OR DETRIMENTAL RELIANCE
Consideration is not necessary if the facts indicate that the promisor should be estopped from not performing. A promise is enforceable if necessary to prevent injustice if:
(1) the promisor should reasonably expect to induce action or forbearance;
(2) of a definite and substantial character;
(3) and such action or forbearance is in fact induced.
The above is from 1st restatement, 2nd restatement omits the definite or substantial character element. Under 1st restatement, a court will award expectation damages (what was promised under the contract), whereas a court following the 2nd restatement would award reliance damages which is usually less than expectation, but in theory could exceed them.