An ingestible device, comprising: a housing comprising an interior and one or more openings; a gas cylinder in the interior of the housing, the gas cylinder having a breakable seal; a spring in the interior of the housing; a piston in the interior of the housing; a piercer in the interior of the housing; a retainer; and a trigger exposed to an environment external to the housing, wherein, in a first state of the ingestible device: the trigger holds the retainer in a first position; the retainer holds the piercer in a first position in which the piercer does not break the breakable seal of the gas cylinder; and the interior of the ingestible device is configured to contain a dispensable substance without the dispensable substance being delivered from the ingestible device via the one or more openings in the housing, and wherein, in a second state of the ingestible device: the trigger is at least partially dissolved, degraded and/or eroded so that the trigger is unable to hold the retainer in its first position; the retainer is unable to hold the piercer in its first position; the spring applies a force to the piercer to move the piercer so that the piercer breaks the breakable seal of the gas cylinder; a gas is released from the gas cylinder; the gas applies a force to the piston so that the piston applies a force to the dispensable substance; and the dispensable substance is delivered out of the ingestible device via the one or more openings in the housing, wherein: the ingestible device further comprises a second piston configured so that, when the first piston applies the force on the dispensable substance, the dispensable substance applies a force on the second piston to slide the second piston to expose the one or more openings and the dispensable substance is forced out of the ingestible device via the one or more openings. a housing comprising an interior and one or more openings; a gas cylinder in the interior of the housing, the gas cylinder having a breakable seal; a spring in the interior of the housing; a piston in the interior of the housing; a piercer in the interior of the housing; a retainer; and a trigger exposed to an environment external to the housing, wherein, in a first state of the ingestible device: the trigger holds the retainer in a first position; the retainer holds the piercer in a first position in which the piercer does not break the breakable seal of the gas cylinder; and the interior of the ingestible device is configured to contain a dispensable substance without the dispensable substance being delivered from the ingestible device via the one or more openings in the housing, and wherein, in a second state of the ingestible device: the trigger is at least partially dissolved, degraded and/or eroded so that the trigger is unable to hold the retainer in its first position; the retainer is unable to hold the piercer in its first position; the spring applies a force to the piercer to move the piercer so that the piercer breaks the breakable seal of the gas cylinder; a gas is released from the gas cylinder; the gas applies a force to the piston so that the piston applies a force to the dispensable substance; and the dispensable substance is delivered out of the ingestible device via the one or more openings in the housing, wherein: the ingestible device further comprises a second piston configured so that, when the first piston applies the force on the dispensable substance, the dispensable substance applies a force on the second piston to slide the second piston to expose the one or more openings and the dispensable substance is forced out of the ingestible device via the one or more openings. the trigger holds the retainer in a first position; the retainer holds the piercer in a first position in which the piercer does not break the breakable seal of the gas cylinder; and the interior of the ingestible device is configured to contain a dispensable substance without the dispensable substance being delivered from the ingestible device via the one or more openings in the housing, and wherein, in a second state of the ingestible device: the trigger is at least partially dissolved, degraded and/or eroded so that the trigger is unable to hold the retainer in its first position; the retainer is unable to hold the piercer in its first position; the spring applies a force to the piercer to move the piercer so that the piercer breaks the breakable seal of the gas cylinder; a gas is released from the gas cylinder; the gas applies a force to the piston so that the piston applies a force to the dispensable substance; and the trigger is at least partially dissolved, degraded and/or eroded so that the trigger is unable to hold the retainer in its first position; the retainer is unable to hold the piercer in its first position; the spring applies a force to the piercer to move the piercer so that the piercer breaks the breakable seal of the gas cylinder; a gas is released from the gas cylinder; the gas applies a force to the piston so that the piston applies a force to the dispensable substance; and the dispensable substance is delivered out of the ingestible device via the one or more openings in the housing, wherein: the ingestible device further comprises a second piston configured so that, when the first piston applies the force on the dispensable substance, the dispensable substance applies a force on the second piston to slide the second piston to expose the one or more openings and the dispensable substance is forced out of the ingestible device via the one or more openings.